Former U.S. Sen. Arlen Specter of Pennsylvania is fighting for his life after being recently diagnosed with a form of cancer.

Specter, 82, had battled cancer before his most recent diagnosis, having undergone treatment for Hodgkin's lymphoma in 2005.

The cancer the former Pennsylvania senator is battling now is a new form, according to CNN, which cited a source close to Specter's office. The network said Specter had "a big flareup" of the condition Monday night, according to the source.

Specter, a moderate Republican who switched allegiances to the Democratic Party in 2009, had a 30-year career in the U.S. Senate - the longest tenured senator in Pennsylvania history.

Specter lost the 2010 Democrat primary in his bid to hold on to his Senate seat. The winner of that contest, former U.S. Rep. Joe Sestak, lost to Republican Pat Toomey in the general election.

In his brief post-Senate career, Specter has been a critic of the Republican Party, which he abandoned in 2009 because he believed the GOP had swung too far to the right.

"The Republican Party has moved so far to the right, you can't recognize Mitt Romney. What Mitt Romney will appear in October? Bill [Maher] had it exactly right; he said that Mitt Romney has changed positions more often than a pornographic movie queen," Specter said during on MSNBC's "Morning Joe" back in March.

The former Pennsylvania senator also wrote his memoirs, "Life Among the Cannibals," about his experience on Capitol Hill.

Specter's book was unabashed, as he said former 2008 Republican vice presidential nominee Sarah Palin as "radiated sensuality," compared late Sen. Ted Kennedy's weight to a walrus and divulged that Federal Reserve Chairman Ben Bernanke dressed like a "hobo" when he wasn't working.