Rep. John Murtha (D-PA 12), an 18-term congressman from southwestern Pennsylvania, died today at age 77. He had been hospitalized for complications related to gallbladder surgery.

Murtha's death comes just days after he became the longest-serving member of Congress in Pennsylvania history. Murtha represented the 12th District since winning a special election in February 1974. Beginning with his election to a full term later that year, Murtha never won re-election with less than 58 percent of the vote.

Murtha's passing will set the stage for the seventh House special election in the 111th Congress, in a district that was evenly split in 2008 between John McCain and Barack Obama. Murtha had faced his toughest race that year as well, on the heels of a controversial remark about people in his district being "racist." He's also been the subject of scrutiny over earmarks he's secured for his Johnstown-based district.

This year, Murtha was facing a primary challenge from Ryan Bucchianeri, a former Naval officer and placekicker on the Navy college football team. Republican Bill Russell, whom Murtha defeated with 58% in 2008, is running again, as is Republican businessman Tim Burns.

Whoever replaces Murtha will have the impossible task of filling in for one of the more powerful members of Congress. Murtha, the first Vietnam veteran elected to Congress, was an Approprations committee "Cardinal" -- a title given to the chairmen of the various Appropriations subocommittees. Murtha chaired the Subcommittee on Defense.

The area that now makes up the 12th District was heavily Republican from the Civil War to the 1930s, according to the Almanac of American Politics. Without Murtha, it is the quintessential swing district. McCain won it by fewer than 1,000 votes; John Kerry won it by 8,000 votes four years earlier.

Democrats have won every special election in this Congress, including one pick-up from the GOP in New York 23. Another is set in the Florida 19th on April 13, with yet another seat opening soon when Rep. Neil Abercrombie (D-HI) steps down to run for governor.

--Mike Memoli and Kyle Trygstad