The nationally watched U.S. Senate primary between incumbent Arlen Specter and his Democratic rival, Rep. Joe Sestak, sits atop the agenda as Pennsylvania voters go to the polls today to select party nominees for a whole raft of offices, including governor and lieutenant governor.

Polls open at 7 a.m. and close at 8 p.m. for the 4.3 million Democrats and 3.1 million Republicans enrolled to vote.

An additional 1 million independents may cast a vote only if there is a ballot referendum in their area. One such question, in Philadelphia, will ask voters if they want to abolish the Board of Revision of Taxes, which has been plagued with controversy over its handling of property-tax assessments.

A Franklin and Marshall College poll, conducted May 3 to 9, projected voter turnout at 38 percent among Democrats and 42 percent among Republicans. But some analysts have said they would be surprised if voter participation was that high.

The Senate race, in which the 80-year-old Specter is seeking nomination to a sixth term, is seen nationally as test of the anti-incumbency mood that has swept much of the country.

President Obama, Gov. Rendell, and most other top Democrats have weighed in for Specter, who switched parties last year.

In order to challenge Specter, Sestak decided not to run for a third term as the U.S. representative from Seventh District in Philadelphia's western suburbs. Each party will nominate a candidate to succeed him in January.

Polls show the Democratic Senate race to be a dead heat.

In the Republican Senate primary, former Rep. Pat Toomey of the Lehigh Valley is viewed as the heavy favorite over longtime antiabortion advocate Peg Luksik of the Johnstown area in Western Pennsylvania.

The primary winners will face off in the Nov. 2 general election.

The intensity of the Senate race, at least on the Democratic side, has stood in marked contrast to the relatively low-key primary contests for governor in each party.

The two races "are night and day," said Christopher Borick, a political analyst at Muhlenberg College.

"The Senate race appears as close as a race can get, while on the governor side . . . one candidate has emerged in front and has not looked back," he said.

With Allegheny County Executive Dan Onorato holding a strong and consistent lead over three opponents in Democratic polls - and with no major issues driving the race - many voters have remained uncommitted until near the end.

State Sen. Anthony Hardy Williams of Philadelphia, running all-out to catch up, received a $1.63 million donation Friday from a political action committee that likes his stance in favor of school vouchers. He poured the money into last-ditch TV and radio ads and into his get-out-the-vote effort.

State Auditor General Jack Wagner of Pittsburgh and Montgomery County Commissioner Joe Hoeffel - the other Democrats in the field - hope Williams succeeds in dragging Onorato back to the pack. That could give them a shot, too.

In the Republican primary, state Attorney General Tom Corbett appears in strong position to win nomination over State Rep. Sam Rohrer of Berks County.

Corbett, of suburban Pittsburgh, has been airing TV ads in an effort to cement his lead. Rohrer has been running a ground-up campaign, hoping that the thousands of people who have turned out at his town-hall meetings will rally their friends and neighbors to vote for him.

The contests for lieutenant governor - featuring three Democrats and nine Republicans - have been even more low-key.

Voters will also nominate candidates for all 19 of the state's U.S. House seats, half its 50 state Senate seats, and all 203 seats in the state House.

In the Sixth U.S. House District, west of Philadelphia, physician Manan Trivedi and former Inquirer editorial board member Doug Pike are locked in the suburbs' hardest-fought battle. Each hopes Democratic voters will nominate him to challenge Republican U.S. Rep. Jim Gerlach in the fall.

Voters will also select members of party committees at the township and neighborhood level.

In Philadelphia, the city and state GOP are battling over party committee slots. State Republican leaders hope they can gain enough committee members loyal to them to later vote out the current leadership, headed by Michael P. Meehan.

The Committee of Seventy, a nonpartisan election oversight group in Philadelphia, said voters who encounter problems at the polls should call the group for help and advice at 1-866-687-8683.

Trained volunteers from the group's headquarters will go into the field to investigate complaints of election impropriety, the committee said.

Contested Primary Races

These offices will be up for election Tuesday. Also on the ballot will be races for the state Senate and House.

U.S. Senate

Democrat

Joe Sestak

Arlen Specter*

Republican

K. Peg Luksik

Pat Toomey

Governor

Democrat

Joseph Hoeffel

Dan Onorato

Jack Wagner

Anthony Hardy Williams

Republican

Tom Corbett

Samuel Rohrer

Lieutenant

Governor

Democrat

H. Scott Conklin

Jonathan Saidel

Doris Smith-Ribner

Republican

Chet Beiler

Jim Cawley

Russ Diamond

Steve Johnson

John Kennedy

Billy McCue

Daryl Metcalfe

Jean Pepper

Stephen Urban

U.S. House

Sixth District

Democrat

Doug Pike

Manan Trivedi

Republican

Jim Gerlach*

Patrick Sellers

Eighth District

Republican

Gloria Carlineo

Michael Fitzpatrick

Ira Hoffman

James Jones

13th District

Republican

Carson Adcock

Brian Haughton

Joshua Quinter

15th District

Republican

Mat Benol

Charles Dent*

* Incumbent

EndText

Contact staff writer Tom Infield at 610-313-8205 or tinfield@phillynews.com.