WASHINGTON (AP) — A resurgent Rick Santorum won Republican presidential contests in Minnesota, Colorado and Missouri in a stunning sweep that raised new questions about front-runner Mitt Romney’s appeal to conservatives and threatened to drag out the race to find a challenger to President Barack Obama.

The victories by Santorum, a fierce and vocal opponent of abortion and gay rights, exposed Romney’s longtime struggles to convince cultural conservatives that he’s now in line with their beliefs despite his previous support as Massachusetts governor of gay and abortion rights.

Santorum cast the results in Tuesday’s contests as a victory for a purer form of conservatism than Romney has offered. Before the Colorado caucus results were announced, a jubilant Santorum declared to cheering supporters in St. Charles, Missouri: “Conservatism is alive and well in Missouri and Minnesota!” Challenging his rival, Santorum said, “On health care, global warming and the Wall Street bailout, he charged, “Mitt Romney has the same positions as Barack Obama.”

Romney shrugged off his poor showing, but his losses in all three contests laid bare his stubborn weakness just when it looked as if his party was beginning to embrace him.

WATCH RICK SANTORUM’S VICTORY SPEECH:

Visit msnbc.com for breaking news, world news, and news about the economy

The revived questions about Romney’s appeal with conservatives at the party’s core were even sharper in light of his aggressive push to court them in recent days. And the Republican nomination fight many in the party hoped would soon resolve itself now threatened to rumble past March 6, or Super Tuesday, when 10 states hold nominating contests. Meanwhile, Obama patiently watches from the White House as his would-be rivals batter each other.

Romney showed no sign of disappointment with Tuesday’s results in remarks to supporters.

“This was a good night for Rick Santorum. I want to congratulate Sen. Santorum, but I expect to become the nominee with your help,” he told supporters in Denver.

In the 2008 presidential race, Romney prevailed in the nominating contests in Minnesota and Colorado, but the Republican Party has become more conservative in both states since then.

Sensing the threat from Santorum, Romney’s team had worked to lower expectations in the run up to voting in the three states and the candidate himself had started emphasizing his positions on social issues like abortion and gay rights in the days since he won Saturday’s Nevada caucuses.

The victories were the first for Santorum since he eked out a 34-vote win over Romney in the leadoff Iowa caucuses a month ago.

Santorum had faded far from the lead in the primaries and caucuses since Iowa, and Newt Gingrich, the former speaker of the House of Representatives, seemed to eclipse him as the leading conservative rival to Romney when he won the South Carolina primary late last month.

Tuesday’s results were grim for Gingrich, who made scant effort in any of the states that voted during the day. He ran far off the pace in the two caucus states, forced to watch from the sidelines while Santorum boasted of being the candidate with conservative appeal.

The former House speaker lacked the resources and organization to compete just as he’s trying to project strength heading into the multiple primaries on March 6. He made only minimal efforts in the three states that voted and stayed out of sight as the results rolled in. Gingrich was campaigning in Ohio, where early voting has begun in the March 6 primary.

Libertarian-leaning Texas congressman Ron Paul, meanwhile, reveled in his second-place win in Minnesota and vowed to keep collecting delegates to take to the Republican Party national convention in late August in Tampa, Florida.

Returns from 95 percent of Minnesota’s caucus precincts showed Santorum with 45 percent support, Paul with 27 percent and Romney with 17 percent. Gingrich trailed with 11 percent.

It was closer in Colorado, where returns from all the precincts showed Santorum with 40 percent of the vote to 35 percent for Romney. Gingrich had 13 percent, and Paul claimed 12 percent.

With all the precincts counted in Missouri, Santorum had 55 percent of the vote, followed by Romney with 25 percent. Paul had 12 percent, while Gingrich wasn’t on the ballot.

The Missouri primary was non-binding with no delegates at stake, Missouri’s delegates to the party’s national nominating convention will be chosen in caucuses beginning next month.

There were 37 Republican National Convention delegates at stake in Minnesota and 33 more in Colorado, and together, they accounted for the largest one-day combined total so far in the race for the Republican nomination.

Santorum campaigned aggressively in all three states holding contests Tuesday, seeking a breakthrough to revitalize a longshot campaign that had struggled since Iowa. He won Minnesota largely the way he did neighboring Iowa, dispatching his organizers from the first state to the second and courting evangelical pastors and leaders of the tea party movement which advocates limited government and low taxes.

But Santorum remains a longshot for the nomination because Romney has an overwhelming advantage in campaign funds, organizational strength and support from the party establishment.

Republican Sen. Roy Blunt of Missouri, a Romney supporter, congratulated Santorum, but added “Mitt Romney has the organization and the resources to go the distance in this election.”

Santorum’s victories in Minnesota and Colorado gave him at least 28 delegates, pushing him past Gingrich into second place in the delegate count. Romney got at least six delegates.

Overall, Romney has 107 delegates, including endorsements from members of the Republican National Committee who automatically attend the party’s national convention and can support any candidate they choose. Santorum has 45 delegates, Gingrich has 32 and Paul has nine.

Following Maine’s low-profile caucuses, which conclude Saturday, the candidates will have an extended lull until contests in Michigan and Arizona on Feb. 28. Then comes March 6 when 10 states hold nominating contests with 416 convention delegates at stake. Georgia, where Gingrich launched his career in Congress, is the biggest prize that night with 76 delegates. Next is Ohio, which has 63 delegates at stake.

___

Associated Press Writers David Espo in Washington and Philip Elliott in St. Charles, Missouri, contributed to this report.

Copyright 2012 The Associated Press.