This year more congressional incumbents are running for their political lives not against an ideological opponent, but from their own kind, competitors in their own party.

So far this year, five incumbents have lost their primaries, three of them to colleagues after their districts were merged or eliminated. The other two lost over scandals and bad blood among party operatives at home.

"The district that was drawn was very tough," said Dan Lucas, chief of staff for Rep. Tom Sawyer, D-Ohio, who lost to state Sen. Tim Ryan after 40 percent of Sawyer's old district, including the area in which he lived, was merged by the state Republican-led legislature into another district far away from his home base. He lost by a 41 to 28 percent margin.

"They took him and put him in a part of the state he never represented — they didn't know him," Lucas said Thursday.

Some incumbent races centered on the classic money advantage, while others got into good old-fashioned mudslinging.

In Pennsylvania, Democratic Rep. Ed Murtha, who has been in office since 1974, trounced four-term GOP Rep. Frank Mascara 65 to 35 percent in a bitter campaign that Murtha said he will not soon forget.

"There are hard feelings," Murtha said of the campaign that saw both men trading frequent attack ads and barbs in the press. "I don't usually take it personally, but I've taken this stuff personally."

Five-term Rep. Brian Kerns, R-Ind., lost to Rep. Steve Buyer, R-Ind., in a May primary that was not so ugly as it was expensive. Buyer had a 3-1 financial advantage over Kerns, a House freshman, but said no hard feelings emerged.

"You work together in Washington, D.C., and come back to Indiana to campaign, so we kept it positive," said Buyer, who got a congratulatory call from Kerns two hours after the polls closed.

Not all incumbents are vulnerable because of redistricting, however. Some are being challenged by astute, popular candidates.

Five-term Rep. Ed Hilliard, D-Ala., lost to attorney Artur Davis by a 56 to 44 percent margin in a June primary that got heated over charges that Hilliard was sympathizing with terrorists and Davis was a patsy for the Republican Party. Both men, who are black and appealed to the Birmingham district's base, raised considerable money from Muslim and Jewish groups from outside the state in this proxy battle over Mideast politics.

Of course, there is always the case where a candidate is responsible for his own undoing. Democratic Rep. Gary Condit, a popular seven-term California congressman, lost his primary against state Rep. Dennis Cardoza more because of his alleged affair with murdered intern Chandra Levy than redistricting in his home district.

At least one lawmaker has chosen to resign rather than enter into the primary bloodbath. Rep. Ben Gilman, R-N.Y., announced his retirement last week in an effort to avoid a primary against Rep. Sue Kelly, a fellow Republican. Both had been redistricted into territory that favored Kelly.

The 30-year veteran said he blamed partisan politics for redrawing him out of a job.

"Redistricting is not supposed to be about politics," Gilman said, referring to the Democrats in charge of the map drawing. "The state's efforts to target our district in order to protect other incumbents undermined our efforts to successfully pursue another term in the Congress."

Before the primary season ends, several more incumbents will face tough challenges.

In Georgia, conservative Republican Rep. Bob Barr has been forced to play down his "attack dog" image as he battles fellow conservative Republican Rep. John Linder in a new district that strongly favors Linder. While both men reflect well the staunchly conservative area, Linder has been more low-key than Barr, who became famous for his support of former President Clinton's House impeachment in 1999.

"This is not a district of Clinton haters," Linder said recently. The primary is in August.

Rep. Cynthia McKinney, D-Ga., is being challenged in a tough fight by Judge Denise Majette, who wants to capitalize on the congresswoman's recent slippage in popularity following a series of controversial public statements.

And the House dean, Rep. John Dingell, the longest-serving representative will have to battle Rep. Lynn Rivers in an August primary. Fellow Michigan Rep. John Conyers proposed last month that Dingell not run, and when Democrats take back the House, reclaiming the seven seats they need to do so, Dingell could be elected the first non-member House speaker.

Dingell declined, saying that he will run for the office that he wants.

The Associated Press contributed to this report.