Voters set to choose in crucial primary election

Voters in Pennsylvania will finally choose between Barack Obama and Hillary Clinton in today’s critical contest in the race to the White House.

The former first lady, who must pull off a significant victory in the Keystone State to keep her campaign alive, will try to reduce her rival’s national lead by winning the majority of the 158 delegates on offer.

Last night, after more than six weeks of intense campaigning in the state, both Mrs Clinton and Mr Obama appeared on the “Raw” WWE wrestling show on US television.

Both candidates declined the offer to settle their contest in the ring, but back on the campaign trail the race descended into the most negative moments of its 16-month primary season.

Mrs Clinton accused her rival of aiding Republican John McCain’s campaign while Mr Obama described her as a compromised Washington insider at a time when most observers agree the nation is demanding change.

Mr Obama sharpened his tone and flooded the Pennsylvanian airwaves with ads on the eve of the state’s crucial primary election.

The young Illinois senator, who trails Mrs Clinton in polls in the state, was using the full resources of his record-breaking fundraising campaign to outspend the former first lady two-to-one.

Mr Obama, who would be the first black American president if elected in November, said the 60-year-old New York senator was making “eleventh-hour smears paid for by lobbyist money” and added he “doesn’t take money from special interest PACs or Washington lobbyists – not one dime”.

Mr Obama, who has said “if you get elbowed enough, eventually you start elbowing back”, predicted Mrs Clinton would win the state’s contest but that his goal was to keep it close.

“I’m not predicting a win,” he told Pittsburgh radio station KDKA.

“I’m predicting it’s going to be close and that we are going to do a lot better than people expect.”

In her own advert, Mrs Clinton used an image of al-Qaida leader Osama bin Laden - the first Democrat to do so – to ask voters whom they would trust most in the White House on the eve of the contest.

An announcer tells voters the race is for “the most important job in the world”.

“You need to be ready for anything, especially now, with two wars, oil prices skyrocketing and an economy in crisis. Harry Truman said it best, ’If you can’t stand the heat, get out of the kitchen.’ Who do you think has what it takes?” the announcer says at the end, as an image of Mrs Clinton at a rally appears.

Obama campaign spokesman Bill Burton said the advert “plays the politics of fear”.

“It’s ironic that she would borrow the president’s tactics in her own campaign and invoke bin Laden to score political points,” Mr Burton said.

Mrs Clinton also attacked Mr Obama, 46, after he said Mr McCain would make a better president than George W Bush.

“We need a nominee who will take on John McCain, not cheer on John McCain, and I will be that nominee,” she said.

The latest Quinnipiac University Poll showed Mrs Clinton, who would be the first woman president, leading Mr Obama 51%-44% in Pennsylvania, an increase of one percentage point from a week ago.

The survey showed the former first lady’s strength was greatest among women, white Catholic and older voters.

Overall, including almost 500 of the 800 superdelegates who have committed to one of the Democrats, Mr Obama leads nationally 1,646 to 1,508, according to figures from the Associated Press.

But with just nine contests left after Pennsylvania, neither candidate is likely to gain the 2,025 elected delegates needed to clinch the nomination.