Media playback is unsupported on your device Media caption Rick Santorum: Your votes were heard loud across this country

US presidential hopeful Rick Santorum has swept the contests for the Republican Party nomination in Minnesota, Missouri, and Colorado.

Mr Santorum outperformed longtime front-runner Mitt Romney, who has struggled to connect with the party's conservative base.

Supporters in Missouri heard Mr Santorum declare victory for all those "building the conservative movement".

The eventual nominee will face Barack Obama in November's election.

Former House of Representatives Speaker Newt Gingrich hardly campaigned in the three states that voted on Tuesday, and did not even appear on Missouri's ballot.

Analysis These results are quite an upset. Mitt Romney always looked shaky in Minnesota, but he had been expected to take Colorado comfortably. Four years ago when Mr Romney was competing for the Republican nomination, he won Colorado with 60% of the vote. Mr Santorum's campaign will receive an injection of enthusiasm and money in the wake of his victory. In winning big in these three states he has lent some credibility to his claim that he can be a real social and conservative standard-bearer. However he lacks the organisation that is a hallmark of the Romney campaign and his candidacy remains a long shot. Most will still view Mr Romney as the front-runner even after tonight. But dissatisfied, fractious Republican voters - especially those on the socially conservative and religious wing of the party - seem to be telling Mr Romney's rivals: "Don't give up."

Distrust of Romney

In Minnesota's caucuses, with 95% of the vote counted, Mr Santorum was on 45%, while Texas Congressman Ron Paul was on 27% and former Massachusetts Governor Romney had 17%.

In Missouri's primary, with all votes counted, Mr Santorum won with 55%, well ahead of Mr Romney at 25% and Mr Paul on 12%.

After an anxious wait, the Republican Party chairman in Colorado eventually declared Mr Santorum the winner in that state's caucuses, too.

Final results showed Mr Santorum won the state with 40% of votes, with Mr Romney on nearly 35%.

Pitching himself as the only true conservative in the race, Mr Santorum had campaigned hard in Minnesota and Missouri - states with significant blocs of Tea Party and evangelical Christian voters respectively.

Polls had showed him performing well, and predicted the possibility he would win in either or both states. But while Mr Romney's team had sought to manage expectations, they still retained hopes of a Colorado victory.

"Conservatism is alive and well in Missouri and Minnesota," he said before the Colorado results were known. "I don't stand here to be the conservative alternative to Mitt Romney. I stand here to be the conservative alternative to Barack Obama."

US commentators on Santorum wins The results "shook the political world", which believed the Republican race "was finally set on a stable trajectory", writes Jim Ruitenberg in The New York Times In The Washington Post, Dana Milbank argues says Mr Obama's luck gets better after Mr Santorum's wins, as the incumbent can just "sit and watch" while "his opponents are alienating the electorate". After Tuesday's votes Mr Romney "seemed to have lost a little bit of his shine", writes Reid J Epstein in Politico. "The Republican race is still open - at least until Super Tuesday on March 6" with its 10 races, The Los Angeles Times argues.

The former Pennsylvania senator, who had not won a contest since his narrow win in Iowa's caucuses in January, had been viewed as a long-shot candidate.

Tuesday's victories will inject new momentum into his campaign, as he hopes to displace Mr Gingrich as the Mr Romney's main challenger.

Mr Gingrich, who was campaigning in Ohio, told CNN: "I think the big story coming out tonight is going to be that it's very hard for the elite media to portray Governor Romney as the inevitable nominee after tonight's over."

Correspondents say Mr Gingrich's game plan is to ride out February and hang on until March when Southern states come into play. As a former Georgia representative with a long history in the south, his campaign feels he stands a better chance of success in those states.

Long race

In a last-ditch effort to win over social conservatives ahead of Minnesota and Colorado's caucuses, Mr Romney tried to boost his credentials on being anti-abortion, pro-religious freedom and opposed to gay marriage.

During his first run for the Republican presidential nomination back in 2008, when he challenged John McCain, Mr Romney won in both Colorado and Minnesota.

But both states are perceived to have moved to the right since then, so doubts over his Mormon faith and political record as governor of a liberal state could have cost him votes.

Latest results Candidates Colorado Minnesota Missouri Table ordered by Colorado results Source: Associated Press Santorum 40.2% 44.9% 55.2% Romney 34.9% 16.9% 25.3% Gingrich 12.8% 10.7% 7.3% Paul 11.8% 27.2% 12.2%

Playing down the significance of Tuesday's contests, Mr Romney told supporters in Denver: "This was a good night for Rick Santorum. We'll keep on campaigning down the road, but I expect to become our nominee with your help.

"When this primary season is over, we're going to stand united as a party behind our nominee to defeat Barack Obama."

Thirty-seven delegates were at stake in Minnesota and 33 Colorado, although they are not officially awarded until later this year. The primary in Missouri is being dubbed a "beauty contest" since it will actually allocate its delegates via a caucus held next month.

Before Tuesday's votes, Mr Romney had 101 of the 1,144 delegates needed to clinch the nomination at the Republican Party convention in August, according to an Associated Press news agency tally.

In second place, Mr Gingrich was on 32 delegates, Mr Santorum 17 and Mr Paul nine.