Rick Santorum quits Republican presidential campaign

Santorum (pictured) faced a tough fight in his home state against rival Mitt Romney (Reuters)

Bowing to the inevitable, Rick Santorum quit the presidential campaign today, clearing the way for Mitt Romney to claim the Republican nomination.

Mr Santorum, appearing with his wife and family in his home state of Pennsylvania, told supporters the race for him was over, but the fight to defeat president Barack Obama would go on.

Mr Santorum made no mention of Mr Romney, and stressed that he had gone further than anyone expected, competing "against all odds".

The delegate totals told the tale of Mr Santorum's demise. Mr Romney has more than twice as many delegates as Mr Santorum and is on pace to reach the number needed to clinch the nomination - 1,144 - by early June.

Still in the race, but not considered a factor are former House Speaker Newt Gingrich and Ron Paul of Texas.

He made no mention or endorsement of Mr Romney, whom Mr Santorum had derided as an unworthy standard-bearer for the Republicans.

The former Pennsylvania senator said: "We are going to continue to go out there and fight to defeat president Barack Obama."

Mr Santorum spoke to Mr Romney ahead of his announcement, a Republican source close to the campaign said.

Mr Romney congratulated Mr Santorum on his campaign, calling him an "able and worthy competitor".

Mr Santorum had been hoping to hold out through the primary in Pennsylvania on April 24, but he decided to fold up after spending the weekend at home with his severely ill three-year-old daughter Bella.

Mr Santorum, a feisty campaigner who took everyone by surprise with his win in Iowa's lead-off caucuses, ran on his conservative credentials. But he was hobbled by a lack of money and organisation.

Mr Santorum stressed the improbable accomplishment of the past year, saying that "against all odds, we won 11 states, millions of voters, millions of votes".

He said that while Mr Romney was accumulating more delegates, "we were winning in a very different way. We were touching hearts" with his conservative message.

In a statement, Mr Romney said Mr Santorum "has proven himself to be an important voice in our party and in the nation. We both recognise that what is most important is putting the failures of the last three years behind us and setting America back on the path to prosperity."

Mr Santorum was a favourite of the most conservative Republican voters, but Mr Romney, the former Massachusetts governor, had accumulated a huge lead in delegates to the party's national convention in August.

Mr Romney's conservative credentials are suspect among the conservative Republican base, but Mr Santorum's inability to put together primary election victories in key states - especially in the industrial Midwest - appeared to have convinced most voters that Mr Romney's nomination was inevitable.

Mr Santorum was the only Republican in what started out as a crowded field who was able to create a sustained challenge to Mr Romney, who is making his second run for the nomination. The distaste that conservatives felt for Mr Romney showed itself in a series of runs at his front-runner status by Rep Michelle Bachmann, Texas Gov Rick Perry, businessman Herman Cain and former speaker of the House of Representatives Newt Gingrich.

Mr Gingrich today said he would stay in the race until the party's convention.

Mr Santorum was to have returned to the campaign trail Tuesday after his daughter was released from hospital. She suffers from a rare genetic condition and was taken to hospital on Friday as her father began a brief holiday break from campaigning. She was discharged from the hospital last night.

He said her latest spell in hospital led him and his family to decide against continuing in the race.

Five states, including Pennsylvania, hold primaries on April 24

President Barack Obama, meanwhile, stepped up his election-year insistence that the wealthy pay a greater share of taxes, renewing his call today for Congress to raise taxes on millionaires.

Hoping to draw a sharp contrast with Mr Romney, Mr Obama outlined his support for the so-called "Buffett rule" in Florida. Mr Obama says he wants to revamp the US tax law under which wealthy investors often pay taxes at a lower rate than middle-class wage-earners.

The push for the Buffett rule is named after billionaire investor Warren Buffett, who famously said it was wrong for him to be paying a lower tax rate than that levied on his secretary.

Mr Obama has proposed that people earning at least 1 million dollars (£630,000) annually, whether in salary or investments, should pay at least 30 per cent of their income in taxes. Many wealthy taxpayers earn investment income, which is taxed at 15 per cent, allowing them to pay a smaller percentage of their income in taxes. The top rate for taxpayers with high incomes derived from wages is 35 per cent.