Michigan Sen. Carl Levin, D, a mainstay of the upper chamber since 1979, will not seek re-election next fall, he said Thursday.

Levin, the chairman of the Senate Armed Services Committee, announced in a statement that he would not seek a seventh term in 2014. Levin is currently 78-years-old.

"As Barbara and I struggled with the question of whether I should run again, we focused on our belief that our country is at a crossroads that will determine our economic health and security for decades to come," he said. "We decided that I can best serve my state and nation by concentrating in the next two years on the challenging issues before us that I am in a position to help address; in other words, by doing my job without the distraction of campaigning for re-election."

Levin was the fifth-most-senior Democrat remaining in the Senate, a legislative body that's undergone tremendous turnover in recent years following the deaths and retirements of some of its most senior members.

Late Thursday President Barack Obama thanked Levin in a statement, praising his work on behalf of the blue-collar workers he represented not only in the Wolverine State, but throughout the country.

"If you've ever worn the uniform, worked a shift on an assembly line, or sacrificed to make ends meet, then you've had a voice and a vote in Senator Carl Levin," read the statement. "No one has worked harder to bring manufacturing jobs back to our shores, close unfair tax loopholes, and ensure that everyone plays by the same set of rules."

Democrats are regarded as having an advantage in holding onto Levin's seat, since Michigan is a state that has tended toward Democrats in statewide and national elections in recent cycles. Moreover, Republicans' bench in the state is regarded as relatively thin.

Levin's older brother, Sander, is a high-ranking congressman from Michigan.

Michigan's congressional delegation met Monday with Gov. Rick Snyder, asking him to veto or at least delay a vote on a "right to work" law moving through the state's legislature.

Democrats and organized labor groups have launched an all-out blitz they are hoping might halt legislation that would establish workers' rights to employment in a workplace without having to join a union. The Republican-held state legislature passed versions of the legislation last week, and are set to bring it up for final consideration as soon as Tuesday.

Snyder, a first-term Republican governor who's fashioned himself as a more pragmatic leader, has said he would sign the bill if it came to his desk.

"We strongly urged the governor to veto the so-called right to work bill, or at a minimum, ask the legislature to delay the vote on it," Sen. Carl Levin said in a conference call to describe Democrats' meeting with the governor. "The governor listened, and he told us that he would 'seriously,' in his words, consider our concerns."

Snyder's office had no immediate reaction to Democrats' characterization of the meeting.

Michigan has become the latest Midwestern epicenter over labor rights as a result of this fight, following Ohio and Wisconsin. The Republican governors of those states led efforts to curb or eliminate collective bargaining rights for public employees' unions.

Alex Wong / Getty Images

Senate Armed Services Committee Chairman Carl Levin

National Democrats have begun to wade into the fight as well, issuing blistering statements warning against the Michigan proposal. The fight could be elevated further this afternoon, when President Barack Obama visits the Detroit area in a previously-scheduled trip.

Democrats are particularly incensed by a procedural move used by Republican authors of the bill which would prevent the law from being challenged by a statewide referendum. The Democrats who met Monday with Snyder said they had also urged the governor to change that provision, so that the right to work proposal could be brought to a popular vote.

JPMorgan Chase CEO Jamie Dimon described his company's $2 billion trading loss as "terrible, egregious mistakes," adding, "there's almost no excuse for it."

Although Dimon had what CNBC Analyst Andrew Ross Sorkin called a "mea culpa" moment about the errors, the JPMorgan CEO was optimistic about the future of the bank. 

"This is not a risk which is life threatening to JPMorgan," he said.

Senator Carl Levin (D-MI) also joined the program to respond to Dimon's comments and made the case that more government regulation could have prevented the loss.

"It could be prevented because these are the kind of bets that put us into the soup to begin with," Levin said. "If we can prevents these kind of bets from being made, we can avoid ever again having to bail out banks."

Gay marriage was also a central part of our discussion this morning. After President Obama announced his support of gay marriage this week, Republican National Committee Chairman Reince Priebus reinforced the Republican position that "[marriage] is between one man and one woman."

You can watch the entire program on our website including our political roundtable for more on the gay marriage debate and what role it will play in the 2012 election. We were joined by: Lt. Governor of California Gavin Newsom; Chairman of the American Conservative Union Al Cardenas; Washington Post columnists Kathleen Parker and Jonathan Capehart; and MSNBC’s Chris Matthews.

Also, you can watch my full PRESS Pass conversation with Jamie Dimon about the economic recovery, politics and how to get America working again.

We'll be back next week. If it's Sunday, it's Meet the Press.

Sen. Carl Levin and CNBC's Andrew Ross Sorkin discuss JPMorgan Chase's $2 billion trading loss and how it could have been prevented.