Senator Arlen Specter seized headlines in April 2009 by quitting the Republican party to become a Democrat. This week he may grab them again by losing the very reelection bid he had hoped to save.

Specter could become another high-profile casualty of angry voters eager to punish incumbents in a handful of primaries on Tuesday, ahead of November elections in which being "from Washington" may be potent political poison.

"Look here, I had a clear shot at reelection," Specter told CNN's "State of the Union" program on Sunday.

"If I had stayed with the obstructionist Republican caucus, I would have been reelected easily, especially in an out-year when the party out of power is favored."

The contests in Arkansas, Kentucky, Oregon and Specter's home state of Pennsylvania, as well as a special May 22 election in Hawaii, come as recent polls show that the climate for incumbents has not been this toxic since 1994.

President Barack Obama's Republican critics, who routed Democrats that year, have high hopes but face an internal party insurrection by arch-conservative "Tea Party" activists irate over policies like the government's 2008 bailout of big banks.

Democrats face a historic pattern of the sitting president's party losing about two dozen seats in mid-term elections -- and have more swing seats to defend because of victories in 2006 and 2008.

And just one in three voters wants to send their representative back to Washington, according to a Washington Post/ABC survey conducted in late April that spelled trouble for both parties.

Republican Kentucky voters appear set to hand "Tea Party" darling Rand Paul the party's Senate nod over Republican Senate Minority Leader Mitch McConnell's hand-picked favorite, Trey Grayson, Kentucky's secretary of state.

Paul -- whose father, Republican Representative Ron Paul, ran for president in 2008 -- has openly capitalized on disaffection with Washington, repeatedly urging voters to "send some different Republicans" to the capital.

"Being an incumbent this year, of either party, is not a happy thing," former Republican Senate majority leader Trent Lott told reporters on a late April visit to the Capitol.

Specter, 80, has the support of Obama and Pennsylvania's Democratic establishment in his neck-and-neck race against Democratic Representative Joe Sestak, a retired admiral who enjoys the backing of the party's liberal base.

"We're in a dead heat," said Sestak, who predicted that Democratic voters in Pennsylvania "do not want to send back to Washington a career politician who will pursue the broken deal-making" that soured them on politics.

Angry voters "are saying 'a pox on both your houses.' They are voting in response to broken politics, not policy," Sestak told AFP by telephone.

Recent polls show both Specter and Sestak running behind Republican hopeful Pat Toomey.

In Arkansas, vulnerable Democratic Senator Blanche Lincoln enjoys establishment support, an edge in polls, and a vast money advantage over Lieutenant Governor Bill Halter, whom the party's labor union allies support.

The closely watched fights follow a Wall Street Journal/NBC poll packed with grim tidings for Democrats, who have hemorrhaged independent voter support since the 2006 election that gave them control of the US Congress.

Four years ago, independents favored Democrats by a 40-24 percent margin, but Republicans now have a 38-30 percent edge, according to the survey, which had an error margin of plus or minus 3.1 percentage points.

Overall respondents now are evenly split on which party should hold Congress, but voters most committed to casting ballots in November prefer Republicans by a lopsided 56-36 percent margin.

And Democratic pollster Peter Hart, who conducted the survey with Republican pollster Bill McInturff, said Democrats did not appear to be getting help from early signs of an economic recovery or the quick arrest of the failed Times Square bomber.

"A lot has happened," he said, "but the basic dynamic of the 2010 elections seems almost set in concrete."

Sestak disputed that diagnosis, saying Democrats could win back independents who "want to trust again, believe again, that someone can be for public service and not just in service of their own careers" -- a backhanded slap at Specter.

But "it's not just about one incumbent, it's a sense that (Washington) DC is broken," he said.