Factbox: Voter mood puts incumbent U.S. politicians at risk

WASHINGTON (Reuters) - Incumbent U.S. Senators Arlen Specter and Blanche Lincoln face tough re-election battles on Tuesday amid a surge of anti-Washington voter anger that threatens to sweep away incumbents from both parties in November's midterm elections.

Public dissatisfaction that neither the Democrats nor the Republicans are doing enough on the economy, unemployment and to restrain government spending have fueled anti-incumbent sentiment that could topple some of the biggest names in U.S. politics and put Democratic control of Congress at risk.

As the party in power, Democrats are most at risk from the sour mood. But Republicans are also vulnerable with grass-roots conservatives mounting several strong primary challenges to Washington veterans.

Here is a look at some of the high-profile incumbents who face difficult re-election bids this year, when U.S. voters choose all 435 members of the House of Representatives, 36 of 100 senators and 37 of 50 state governors.

* Senate Democratic leader Harry Reid of Nevada

Reid, the most inside of Washington insiders, would be the biggest conquest for Republicans. They accuse him of neglecting Nevada while battling on behalf of President Barack Obama's legislative agenda. Even after a heavy advertising blitz, Reid trails potential Republican opponents by double digits in opinion polls in a state where the economy has nosedived.

* Republican Senator John McCain of Arizona

The 2008 Republican presidential contender has been scrambling to his right to ward off a strong primary challenge from former Representative J.D. Hayworth, an outspoken conservative. McCain, once a moderate on immigration, backs Arizona's tough new immigration law.

* Democratic Senator Arlen Specter of Pennsylvania

Specter, who switched from the Republican Party last year, faces a tough primary challenge on Tuesday from Democratic Representative Joe Sestak. Sestak has closed a double-digit gap in polls by questioning Specter's party credentials. He is airing an ad with the tag line: "Arlen Specter switched parties to save one job -- his, not yours."

* Democratic Senator Blanche Lincoln of Arkansas

The moderate Lincoln also faces a tough primary challenge on Tuesday from Lieutenant Governor Bill Halter, who has mounted a campaign backed by labor unions unhappy with her failure to support legislation making it easier to organize, as well as activists unhappy with her opposition to a public option in the U.S. healthcare overhaul.

* Democratic Senator Barbara Boxer of California

The sour mood has given Republicans a possible opening to knock off the three-term liberal in a Democratic state that has experienced a fiscal crisis, a nasty political fight over the state budget and tax increases. The eventual Republican nominee will emerge from a three-way primary battle on June 8.

* Democratic Senator Michael Bennet of Colorado

Bennet was a Denver public school superintendent with a limited statewide profile when he was appointed to the Senate last year to succeed Ken Salazar, who became the U.S. interior secretary. Bennet has raised a lot of money but faces a tough primary fight from a former Colorado House speaker. If he survives, he will have a difficult race in November, although Republicans have their own contested primary.

* Democratic Representative Ike Skelton of Missouri

The chairman of the House of Representatives Armed Services Committee has never been threatened since entering the House in 1976 but his conservative rural Missouri district voted heavily for McCain in the 2008 presidential election and could be ready to turn on the Democrat.

* Democratic Representative Alan Grayson of Florida

The first-term congressman who represents the Orlando area became a favorite of left-wing blogs and a target for conservative activists last year after he described the Republican healthcare plan as "die quickly." Grayson has thrived on the attention but Republicans are counting on voters in the swing district deciding he is too liberal.

* Republican Representative Joseph Cao of Louisiana

Democrats see Cao's victory in 2008 as a fluke. He narrowly won in a heavily Democratic district with a majority of black voters after Democratic incumbent Bill Jefferson was indicted on bribery charges and the voting was delayed to December by a hurricane, reducing turnout. In November, Cao became the only Republican in Congress to vote for Obama's healthcare overhaul -- but he reversed his stance on the final vote in March.

* Texas Republican Governor Rick Perry

The conservative Perry faces popular former Houston Mayor Bill White, who Democrats consider their best candidate for governor in years. Perry easily beat Senator Kay Bailey Hutchison in the primary, painting her as a Washington insider and has already started lumping White with Obama and the Democratic Congress.

* Massachusetts Democratic Governor Deval Patrick

The surprise election of Republican Scott Brown in a special Senate race in January proved Republicans can win in heavily Democratic Massachusetts. That is bad news for Patrick, a pal of Obama, who has dismal approval ratings after huge tax increases and a series of budget battles with the state legislature.

(Editing by David Alexander and John O'Callaghan)