Published 12:23 p.m. ET -- Although stung by attacks from his former Republican colleagues in the Senate, Chuck Hagel is bracing to fight back against his critics and has no intention of withdrawing as the nominee to be Defense Secretary, according to the former senator's brother.  

"He's not going to walk away from this," said Tom Hagel, who spoke to his older brother about the looming confirmation battle on Sunday night. "The way he's responding to this, he's just going to fight harder." 

Tom Hagel's comments to NBC News came Monday just moments before Sen. Carl Levin (D-MI), chairman of the Senate Armed Services committee, announced the panel will vote Tuesday on Hagel's nomination.

They also came amid mounting signs that some Republican senators are gearing up to try and fight it with a filibuster. On Sunday, South Carolina Sen. Lindsey Graham, a member of the committee, vowed to put a hold on the nomination -- as well as that of John Brennan to be CIA director -- if the administration does not provide more information about the attack on the U.S. consulate in Benghazi. Oklahoma Sen. James Inhofe, the ranking Republican on the Armed Services panel, said he was weighing a filibuster.

But other Republicans senators, including Arizona Sen. John McCain, Roy Blunt (R-MO), and Susan Collins (R-ME) -- have said they would not support a filibuster. It's not clear Graham would have the votes to go through with one.

There was also speculation the former Nebraska senator might pull his name as a result. Widely respected defense analyst Tom Ricks wrote Friday he believed there was a 50-50 chance Hagel would withdraw.

Tom Hagel, who served with his older brother in the Army during Vietnam and sat behind him during his rocky Jan. 31st confirmation hearing, described Chuck Hagel as "committed" and "optimistic"  that he will be confirmed as Defense Secretary.    

"I don't think there is any possibility" he will withdraw-unless he's asked to do so by President Obama, Tom Hagel said.

Chip Somodevilla / Getty Images

Former Senator Chuck Hagel testifies before the Senate Armed Services Committee during his confirmation hearing to become the next secretary of defense on Capitol Hill January 31, 2013 in Washington, DC.

The White House appeared to shoot down any hint of that Monday.

"We are absolutely committed to the Hagel nomination," said Tommy Vietor, a White House spokesman.

Tom Hagel said his brother was "shocked" by the level of personal animosity to his nomination from his former GOP colleagues in the Senate.

He also indicated that both he and his brother were upset about the blizzard of TV ads from anonymously funded advocacy groups attacking his nomination, calling the ads "absolutely gutless." He added, "If these people have integrity and believe in what they are doing, why don't they put their names to it?"

But while his brother was "tired" by the ordeal and it has taken a "personal toll," Tom Hagel said his brother was "ready to deal with it" and prepared "to respond to whatever attacks come out."

The self-described Atlanta-based "oppo researcher" who helped broker the release of the secret video that has rocked the Romney campaign got a congratulatory email today from his famous grandfather -- former President Jimmy Carter.

James Carter IV told NBC News in an interview that, starting late last month, he tracked down the source who took the secret Romney video via Twitter --  and then in a series of messages encouraged him to release the full tape to Mother Jones magazine.

After emailing his grandfather the magazine's story about the tape -- under the subject, "Huge campaign news," and calling it "my biggest story yet" -- the former president wrote back at 7:16 am Tuesday: "James: This is extraordinary. Congratulations! Papa."

"I'm proud of my role in being able to track him down," James Carter, 35,  said about the source who took the video. "I'm a partisan Democrat. My motivation is to help Democrats get elected. If there is anything I can find in any race, I try to do that."

Related: Leaked video is the latest hit for Romney

But Carter also confirmed there is a personal side to the backstory of the campaign video: he was especially motivated, he said, because of Romney's frequent attacks on the presidency of his grandfather, including the GOP candidate's comparisons to the "weak" foreign policy of Carter and Barack Obama.

"It gets under my skin -- mostly the weakness on the foreign policy stuff," Carter said. "I just think it's ridiculous. I don’t like criticism of my family."

Carter said he is currently unemployed and has not been paid for his work by the Obama campaign or any other political organization. What motivated him at first was Romney's role at Bain Capital and the controversy over whether the GOP candidate as a businessman had invested in companies that outsourced jobs overseas.

Carter had focused, in particular, on Bain Capital's 1998 investment -- while Romney was still chief executive -- in Global Tech Appliances, a Chinese manufacturing company. Carter was listed as providing "research assistance" to a July 11 story about the investment by David Corn, Mother Jones' Washington bureau chief and an MSNBC contributor.

Related: Romney: Secretly recorded remarks 'not elegantly stated'

Then, in late August, just before the Republican convention, Carter spotted a YouTube link to a brief video clip in which Romney talks about his investment in a Chinese company. The link was posted under the name "Rachel Maddow" but was quickly taken down because the poster had no relationship to the MSNBC host.

The video then reappeared on YouTube under a different account -- "Anne Onymous." Carter said he was fascinated by the video -- and figured there had to be more to Romney's talk.

"It was just weird video to all of a sudden come across,” he said. “It was all very strange and it piqued my curiosity," he said.

Carter Tweeted a link to the video -- and then soon noticed he had a new follower named "Anne Onymous."

"I recognized it" -- and then messaged the follower back, resulting in a series of exchanges in which he encouraged the poster to come forward and give the full video to Corn.

The source who took the video has confirmed to NBC News that it was taken at a May 17 $50,000-a-plate fundraiser at the Boca Raton, Fla., home of private-equity mogul Marc Leder, chief executive of Sun Capital Advisors.

Leder has given $225,000 to Restore Our Future, the pro-Romney Super PAC, in addition to raising money for Romney's presidential campaign. He has also been the subject of controversy after a report in the New York Post last year -- under the headline "Nude Frolic in Tycoon's Pool" -- about a wild party at his Bridgehampton mansion in which, according to the Post's account, "guests cavorted nude in the pool" and scantily clad Russian dancers performed on platforms.

Leder has not responded to a request for comment from NBC News.

You may have never heard his name, but David Bossie has already done plenty to influence the 2012 election and he’s not finished yet.

Now, the veteran conservative activist, whose political “oppo” movie-making triggered the Citizens United decision by the Supreme Court that unleashed unlimited spending on campaign ads, is planning to make another big splash at this week’s GOP convention.  This week, Bossie will be unveiling a  new $5 million attack film depicting Barack Obama as an out of touch elitist whose presidency has been a complete failure.

The movie , “The Hope and The Change,” is the latest and most ambitious production yet of Citizens United—the conservative advocacy group that Bossie heads. It’s an ideological companion to “2016: Obama’s America,” another anti-Obama movie by conservative writer Dinesh D’Souza that made a surprisingly strong showing in the box office last weekend.

In Bossie’s movie, an advance copy of which he  shared with NBC News, a parade of 40 voters—all of whom say they voted for Obama in 2008 and many with hard luck stories – vent about bailouts, subsidies for the wealthy, health care and their utter disillusionment with the president. 

“There are some really unbelievably powerful moments in this film where you get choked up over,” says Bossie, as he discussed his high hopes for the movie in an interview Sunday.  “ Because these people, they’re your average Americans.  These are average Americans.”

The voters seen in the film weren’t selected by accident. They were culled from thousands of participants in focus groups in key battleground states conducted for Citizens United by  Patrick Cadell, the one- time Jimmy Carter pollster (and now a regular commentator on Fox News.) Cadell  teamed up with Bossie and director Steve Bannon—former executive chairman of Breitbart.com, the website of the late conservative activist Andrew Breitbart--  to make “The Hope and The Change.” 

“It’s really a story of these 40 Democrats and Independents and their lives over the last four years,” says Bossie. “They bought into the hope and change.  They bought into the rhetoric of, ‘I’m a uniter, not a divider.’ ... If conservatives can learn  to talk these people – this group of people – they’re going to be able to win a lot of elections.

Related: First Thoughts: Two storms in two weeks

Not all of the commentary made by the voters in the film would withstand the scrutiny of fact checkers. Several complain about big bail-outs to big  banks (“Nobody came to help me and bail me out,” one says) with no mention that it was actually President Bush, not Obama, who approved the TARP bail-out to banks in late 2008.

But even more arresting moments than the stories of these voters may be  shots in “The Hope and The Change” of adoring, near hysterical crowds watching Obama speeches in 2008 -- images that one critic has already compared to scenes from the movies of Nazi propagandist Leni Riefenstahl.  (Bossie, for his part, rejects the comparison, saying he’s never even seen any of Riefenstahl’s  movies.)

Slideshow: Republican National Convention

As the movie progresses, these are followed by repeated clips of a seemingly carefree  president shooting hoops, playing golf, yucking it up with Hollywood celebrities and taking vacations in Hawaii and Martha’s Vinyard—all while Bossie’s “average Americans” are suffering.

Bossie, who earned his spurs as a congressional investigator on the Whitewater investigation and other Clinton era probes, has invited hundreds to the  world premier of “The Hope and The Change,” Tuesday  afternoon at Liberty Plaza—a sprawling white tent a few blocks from the Tampa Convention Center where Citizens United, the super PAC American Action Network, and a host of other companies and lobbying organizations have set up entertainment centers and rest areas for the delegates and GOP lawmakers.

But Bossie says the big impact from his film will become later this week when he announces what he is touting as a “major TV deal” to air his movie on its entirety on cable. (Portions were aired last Friday night on a special Sean Hannity show.) Following that, Bossie says, the movie will be spliced up and turned into Citizens United attack ads that will run right up to election day. 

In producing “The Hope and The Change,”  Bossie says he takes his inspiration from Michael Moore, the famed leftwing filmmaker whose “Fahrenheit 911” skewered then-President George W. Bush before the 2004 election.

Recommended: Republicans ready for convention, but are they ready to attract Latino voters?

Indeed, Bossie says it was Moore who prompted him and Citizens United to do an earlier attack movie on Hillary Clinton that led to the now famous Supreme Court decision rejecting restrictions on big money attack ads in political campaigns.

“Michael Moore made a film attacking George Bush, and he didn’t let the facts get in the way of a good storyline,” says Bossie. “ What we did was want to be able to do the same thing. That’s what the Citizens United case emanated from. .. And that’s why in 2008 I went to the United States Supreme Court to fight for my right, and it took me many years.  And in 2010 we finally won our victory.” 

Now, Bossie says, the legal gloves are off: He can make whatever film he wants, spend as much as he can raise to influence the election (and not tell anybody where the money comes from) and not worry about the Federal Election Commission coming after him.

“This is the first election cycle that we are now legally able to make a political documentary and show it and its ads on television,” he says. “And we’re really excited about that.”

A super PAC backing Mitt Romney has just made nearly $6 million in new ad buys in South Carolina and Florida in an apparent attempt to blow away the GOP frontrunner's opponents by the end of the month.

A source close to Restore Our Future, the pro-Romney super PAC, confirmed that in the last few days it has bought up $2.3 million of media time in South Carolina and another $3.6 million in Florida to run ads in those states.

Read more reporting from Michael Isikoff in 'The Isikoff Files'

These buys show the powerful financial muscle behind the Romney group - flush with big donations from wealthy Wall Street investors and others. They also exceed the reported $3.4 million ad buy that Winning Our Future, the pro-Gingrich super PAC, made in South Carolina this week after receiving a $5 million infusion from billionaire casino magnate Sheldon Adelson.

The clash of the rival super PACs that can take unlimited donations from wealthy contributors and corporations - is increasingingly dominating the GOP presidential race. A firm that tracks media buys for NBC News has found that, even before these buys, the Romey super PAC had already spent $7 million on ads in the primaries, exceeding the $5.5 million that was spent by the official Romney presidential campaign.

The super PAC ads are also far more nasty than those being run by the campaigns. In his victory speech tonight, Mitt Romney took a pointed shot at other Republicans who he said were "dividing" the country - a clear shot at blistering ads that the Gingrich super PAC has vowed to run attacking Romney for costing thousands of workers their jobs when he ran the private equity firm Bain Capital.

Rick Tyler, a spokesman for the Gingrich super PAC, said that Romney should stop "whining" about his group's ads - and said they will begin running on South Carolina TV and radio stations by Thursday morning.

"It’s amazing that he would take the opportunity of his victory speech to allow us to get under his skin," Tyler said.