Millions of Americans head for 'Super Tuesday' polls

Millions of Americans in more than 20 states headed to the polls today as record turn-outs were expected in one of the most significant days of the presidential campaign so far.

Hillary Clinton and Barack Obama vied for support within the Democratic Party while Republican John McCain was hoping to emerge as his party’s presumptive nominee when the Super Tuesday results come in.

Mitt Romney, Mr McCain’s closest rival, was out to stop him.

Polls in most states close at midnight Irish Time, but winners in the crucial state of California are not expected to be known until Wednesday morning.

The candidates’ performances will be judged on two aspects – the number of delegates (the people who will choose the nominee at the parties’ national conventions in the summer) and the number of states won.

Both Mrs Clinton, who would be the first woman president, and Mr Obama, who would be the first African American president, are expected to claim victories as soon as possible in a bid to build momentum through national television coverage.

But pundits warned today that California, which will be one of the last states to declare its winners, will be crucial.

Robert Shrum, a Democratic political analyst, told the New York Times: “Don’t be rushed into making an early judgment without California.

“You have to resist the pre-California spin unless someone is winning like 16 of the 22 states.”

If Illinois senator Mr Obama can win in California, where he enjoyed a late surge in the polls to tie the state with the former First Lady, it will be a significant blow to the Clinton campaign.

Along with California, Massachusetts, New York, Missouri, Arizona and New Mexico will all be key.

Senator Ted Kennedy’s recent endorsement of Mr Obama could help him in Massachusetts, where Mrs Clinton once had a comfortable lead in the polls, and an Obama win in her home state of New York, or neighbouring New Jersey, would raise serious questions about her electability in November.

And Missouri, Arizona and New Mexico could go either way, as the pair are close in the polls.

As to who is supporting whom, the results of Georgia and New York will show who is winning the African American vote, while New York and California will offer an insight into Latino voters.

And Mr Obama’s performance in Alabama will give a clearer indication of his support among Southern white voters.

In the Republican contest, California and Massachusetts will again be critical.

Mr McCain’s lead in California, whose governor Arnold Schwarzenegger endorsed him last week, has narrowed recently and a win for Mr Romney in the largest US state would leave him unlikely to pull out of the race soon – regardless of any other results.

And in a sign of Mr McCain’s growing confidence, the Arizona senator has been campaigning in Mr Romney’s home state of Massachusetts.

A McCain win there, along with victory in California, is likely to spell the end for Mr Romney’s presidential aspirations in this campaign.

For the Democrats, the magic number of delegates is 2,025 and 1,681 of these are available today.

Mrs Clinton leads the way at the moment with 48 pledged delegates and an estimated 184 superdelegates, making 232 in total. Mr Obama follows with 63 pledged delegates and an estimated 95 superdelegates, making a total of 158.

For the Republicans, the magic number is 1,191, with 1,020 on offer today.

Mr McCain leads the way with 95 pledged delegates, and an estimated 97 in all, followed by Mr Romney with 85 pledged delegates and an estimated 92 in total.