Specter, Lincoln in jeopardy on big voting day

WASHINGTON (Reuters) - Two veteran senators faced potential career-ending challenges on Tuesday, as voters cast ballots in four state primary contests amid widespread anti-Washington anger ahead of November's midterm elections.

Democrats Arlen Specter of Pennsylvania and Blanche Lincoln of Arkansas faced strong tests from the left, while a U.S. Senate race in Kentucky between a Republican establishment favorite and a conservative "Tea Party" activist tested the strength of that loosely organized conservative movement.

Kentucky will be the first state to close its polls, with voting ending at 7 p.m. EDT in the months-long, state-by-state process of the two parties picking their candidates for November's congressional elections.

The three primary election battles highlighted the biggest day of voting so far in a year when opinion polls find a sour voter mood fueled by distrust of Washington and worries that neither Democrats nor Republicans are doing enough to rescue the economy and restrain government spending.

President Barack Obama, his Democrats bearing the brunt of voter anger, flew to recession-hit Ohio on Tuesday to deliver a message that efforts to revive the economy were bearing fruit, adding 290,000 jobs last month.

"If we hadn't acted, more people in the Mahoning Valley, more people in Ohio and more people across America would be out of work today," Obama told supporters in Youngstown.

The anti-Washington mood, which pollsters say is the strongest in decades, threatens to sweep away many well-known incumbents and put Democratic control of Congress at risk in November's election, when all 435 House of Representatives seats, 36 of 100 Senate seats and 37 of 50 state governorships are at stake.

"If you're an incumbent, it doesn't matter what party you are in -- you better take this seriously. People are angry," said Brad Coker of Mason-Dixon Polling and Research.

Prominent incumbents in each party -- three-term Republican Senator Robert Bennett of Utah and 14-term Democratic Congressman Alan Mollohan -- already failed to win their party nominations in a possible sign of things to come.

Specter, a 30-year Senate veteran and former chairman of the Judiciary Committee, would be the biggest incumbent to go down so far this year if he loses on Tuesday.

He switched from Republican to Democrat last year after calculating that he could not win a Republican primary, but a 20-point lead over Representative Joe Sestak turned into a dead heat as Sestak questioned Specter's party credentials.

'THE ULTIMATE INCUMBENT'

"As we have seen elsewhere this spring, there is an anti-incumbent mood in the electorate and Specter, with 30 years in the Senate, is the ultimate incumbent," Quinnipiac University pollster Peter Brown said.

Democratic officials have rallied to Specter's aid, and he aired an ad featuring Obama praising him. But even with a primary victory, Specter would face a tough re-election fight in November against Republican Pat Toomey.

The polls in Pennsylvania close at 8 p.m. EDT.

In Arkansas, two-term incumbent Lincoln is in a tough primary race with Lieutenant Governor Bill Halter, who has been backed by labor unions unhappy with Lincoln's failure to support a bill making it easier to organize workplaces.

During the debate on an overhaul of financial regulations, Lincoln introduced a tough bill to force investment banks to dump their derivatives businesses in what critics called an overture to the left.

Like Specter, Lincoln faces a tough general election campaign even if she beats Halter. Polls show Representative John Boozman, expected to emerge from a crowded Republican primary, currently leads her in a potential November matchup.

The polls close in Arkansas at 8:30 p.m. EDT.

For Republicans, the Kentucky battle for retiring Senator Jim Bunning's seat pits establishment favorite Trey Grayson -- the handpicked candidate of Senate Republican leader Mitch McConnell -- against Rand Paul, a doctor and son of libertarian Republican Representative Ron Paul.

A victory for Paul, who has been backed by Tea Party groups and leads in recent polls, would be another boost for a Tea Party movement that helped take down Bennett in Utah and drive moderate Governor Charlie Crist out of Florida's Republican Senate primary. Crist will run as an independent in November.

Pennsylvania also will hold a special House election to replace Democrat John Murtha, who died in February. A Republican win would be a first step in their climb toward reclaiming House control -- they need to gain 41 seats in the 435-seat chamber.

(Editing by David Alexander and Paul Simao)