Conservative White House hopeful Rick Santorum surged to two startling, come-from-behind wins on Tuesday in the Deep South, in a dramatic shake-up of the Republican presidential battle.

...he ridiculed Mr Romney’s inability to win over voters in several states despite massively outspending his rivals on campaign advertising

Mr Santorum’s victories in Alabama and Mississippi gave his campaign a huge boost and delivered a stinging rebuke for Mitt Romney in the battle to be the Republican nominee to take on President Barack Obama in November elections.

Mr Romney scored a consolation win in the Republican caucus in Hawaii, Mr Obama’s birthplace

The results were also bad defeats for former House speaker and southern native Newt Gingrich, as the two states were seen as must-wins for his flagging campaign.

Mr Santorum’s sweep of Alabama and Mississippi highlighted how months into the race Mr Romney, still the frontrunner, has failed to seal the deal and convince US voters that he is the strongest candidate to face Democrat Obama.

Mr Santorum trumpeted his conservative credentials after the victories, in a pointed jibe at Romney, who critics have labelled a moderate, liberal former governor of Massachusetts.

“We did it again!” Mr Santorum told ecstatic supporters in Lafayette, Louisiana, where he had travelled after campaigning heavily in Alabama and Mississippi.

“The time is now to make sure, to make sure that we have the best chance to win this election and the best chance to win this election is to nominate a conservative to go up against Barack Obama.”

Mr Santorum said his grassroots campaign consisted of “ordinary folks doing extraordinary things − sort of like America.”

“We will compete everywhere,” he said, as he ridiculed Mr Romney’s inability to win over voters in several states despite massively outspending his rivals on campaign advertising.

With 99 per cent of precincts reporting, Mr Santorum was ahead in Alabama with 35 per cent of the vote, with Mr Gingrich and Mr Romney tied for second place on 29 per cent, according to CNN figures.

In neighbouring Mississippi the race came down to the wire, with Mr Santorum on 33 per cent, Mr Gingrich at 31 and Romney at 30, with 99 per cent of votes counted.

Libertarian congressman Ron Paul of Texas finished a distant fourth in both states.

Mr Romney issued a statement congratulating Mr Santorum on the win, but adamantly insisted he remained best placed to win the nomination.“I am pleased that we will be increasing our delegate count in a very substantial way after tonight,” said Mr Romney, who has about 40 per cent of the 1,144 needed to become the party’s presidential nominee.

“With the delegates won tonight, we are even closer to the nomination,” he added.

All eyes, however, turned to Mr Gingrich, who is fighting to remain viable after winning just two out of the 26 contests held so far. He faces mounting calls to quit and allow conservatives to coalesce around Mr Santorum, but on Tuesday night, while he congratulated Mr Santorum on a “great” double win he indicated he would fight all the way to the Republican convention in Tampa, Florida in August.

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