April 22 (Bloomberg) -- Democrats Barack Obama and Hillary Clinton scrapped for last-minute advantage in today's Pennsylvania presidential primary with a flurry of campaign events and pitches to fans of news, comedy and wrestling.

The two candidates engaged in a fresh round of sparring through television ads and interviews as voters headed to the polls in the biggest contest left in the nomination race.

``I'm going to work as hard as I can between now and the times the polls close to encourage people to get out and vote and make sure that they're going to help pick the next president,'' Clinton said today as she campaigned in the state.

Clinton needs a landslide victory of about 25 points in Pennsylvania, plus 20-point wins in later contests such as West Virginia, Kentucky and Puerto Rico to overcome Obama's more than 800,000-vote lead in popular votes garnered in primaries and caucuses already held.

Polls conducted over the past week showed a close race in Pennsylvania, which has 158 pledged delegates at stake. Clinton supporters, including New Jersey Governor Jon Corzine, say she needs to lead Obama in either delegates or the popular votes by the end of primary balloting in June to make a case that she should be the Democratic nominee. She now trails Obama in the number of delegates needed to win the nomination.

Margins

Clinton said given that Obama has outspent her by 3-to-1 in Pennsylvania, any margin of victory would be good enough.

``A win under these circumstances is a terrific accomplishment,'' the New York senator said after stopping at a polling site in Conshohocken, a mill town near Philadelphia. ``Maybe the question is, why can't he close the deal?''

Obama sought to play down expectations.

``Senator Clinton had a 20-point lead to start with and we think we have closed it, but we still I think have to consider ourselves the underdog,'' Obama said at a diner in Pittsburgh. ``A lot of it, I think, will depend on turnout.''

Voting ends at 8 p.m. local time. Exit polls conducted for television networks showed Clinton was getting 55 percent of women voters and 60 percent of the white vote. Obama led among men with 53 percent and he was getting 92 percent of the black vote.

The polls also showed that 54 percent of voters said they expect Obama will get Democratic nomination, according to data cited by CNN.

Voter Outreach

Illustrating the candidates' efforts to reach every possible voter, Obama, Clinton and Arizona Senator John McCain, who has locked up the Republican nomination, made taped appearances on the World Wrestling Entertainment Inc. program ``Monday Night RAW'' on the cable channel USA Network.

The WWE says the weekly program draws 5 million viewers, and all three candidates used wrestling themes for their messages.

``Tonight, in honor of the WWE, you can call me Hillrod,'' Clinton, 60, said in her segment. ``This election is starting to feel a lot like `King of the Ring.' The only difference? The last man standing may just be a woman.''

Obama, 46, said, ``this is a historic time for America. It's not just that the reign of Randy Orton may soon be coming to an end.'' Orton is the reigning WWE champion.

Obama also appeared on the Comedy Central cable channel program ``The Daily Show'' and Clinton on CNN's ``Larry King Live.'' They both taped interviews with national broadcast networks and local television and radio programs as well.

Ad War

Clinton released a 30-second advertisement in Pennsylvania that included images of the Japanese attack on Pearl Harbor, Fidel Castro and Osama bin Laden.

``It's the toughest job in the world,'' the announcer says as the pictures flash by. It concludes by asking, ``Who do you think has what it takes?''

The ad is similar in theme to the ``3 a.m. phone call'' spot that her campaign advisers regarded as helping Clinton win the Texas primary.

Obama campaign officials responded by accusing Clinton of using scare tactics and countering with an ad of their own.

``Who made the right judgment about opposing the war and had the courage and character to speak honestly about it? And who in times of challenge will unite us -- not use fear and calculation to divide us?'' the announcer in Obama's ad asks.

Interest in the race is high in the state, judging by voter registrations. The Pennsylvania Department of State reported that 4.2 million people have registered to vote as Democrats for the primary, compared with the 3.7 million registered before the primary in 2004. Republican registration was 3.2 million, roughly the same as four years ago.

The next two states to hold primaries are Indiana and North Carolina, which vote on May 6.

To contact the reporters on this story: Lorraine Woellert in Pittsburgh at lwoellert@bloomberg.net; Julianna Goldman in Blue Bell at Jgoldman6@bloomberg.net.

Last Updated: April 22, 2008 19:26 EDT