DENVER, Colo. — Rick Santorum clobbered Mitt Romney in a head-to-head match-up in Missouri’s non-binding primary, easily won Minnesota’s caucuses and snagged a close victory in Colorado’s caucuses in a clean sweep Tuesday that once again rewrote the story of the Republican presidential nomination battle.
None of the three contests leads immediately to any delegates being awarded toward the nominating convention in Tampa, Fla., this summer, but Tuesday’s results suggest a strong pool of support for Mr. Santorum and highlight dangers going forward for Mr. Romney, who had by far his worst showing of the campaign.
Mr. Santorum said he was able to win on Tuesday because Mr. Romney didn’t commit millions of dollars to negative attack ads in these three states. Mr. Santorum said that leveled the playing field.
“Conservatism is alive and well in Missouri and Minnesota,” Mr. Santorum said at his victory party in Missouri, adding, “we doubled him up here, and in Minnesota.” He didn’t say who the “he” was, but there was little doubt it was Mr. Romney — the front-runner whose inability to pull away from the field remains the dominant story of this year’s election.
The Missouri vote was most telling. Newt Gingrich failed to qualify for the ballot, leaving voters with a streamlined choice among Mr. Romney, Mr. Santorum and Rep. Ron Paul. Mr. Santorum took full advantage, winning with 55 percent of the vote — more than any other candidate has won in any of the previous contests.
In Minnesota, his victory was almost as strong, winning 45 percent of the vote. Mr. Paul came in second, leaving Mr. Romney in third place — the first time he’s done that poorly in any of the contests.
And in Colorado, the state party called the race for Mr. Santorum about 11 p.m. local time, delivering the final blow to Mr. Romney, who had expected to at least hold that state.
Mr. Romney, speaking at a party in Denver, congratulated Mr. Santorum but told Republicans he still expects “to become our nominee.”
Minnesota and Colorado combined will be worth 70 delegates to the nominating convention, which will be divvied up at future conventions in each state. Missouri is worth 49 delegates, to be awarded at future caucuses and conventions.
But the key to Tuesday was that the delegates to the state conventions, who will eventually decide the delegates to the national convention, were chosen in each precinct. And that’s where Mr. Paul said he will show his strength.
“The straw vote is one thing, but then there’s one other thing called delegates. That is where we excel,” the congressman said at his party in Minnesota. “When the dust settles, I think there’s a very good chance we’re going to have the maximum number of delegates coming out of Minnesota.”
Mr. Romney began the day with 101 delegates, out of 1,144 needed to secure the nomination, followed by Mr. Gingrich with 32, Mr. Santorum with 17 and Mr. Paul with nine, according to the Associated Press’s tally of delegates already awarded or projected.
Sensing Mr. Santorum’s surge, the Romney campaign turned its fire this week, accusing Mr. Santorum of supporting earmarks while serving as a senator from Pennsylvania. The campaign also released Mr. Santorum’s endorsement of Mr. Romney in 2008. Mr. Santorum contends that Mr. Romney was the conservative alternative to Sen. John McCain in 2008, but that he himself is the conservative choice this time.
Where earlier contests had been fought over the airwaves with increasingly biting ads, the battles in these states were lower-cost affairs.
In Colorado, television ads were rare, but Republicans who answered their phones were greeted by a steady stream of pro-Romney and anti-Santorum robocalls.
“It would really mean a lot to Mitt and me to have your vote at the caucus,” Ann Romney said in a Tuesday call, adding that her husband is “a man of incredible character and honesty.”
Mr. Gingrich and Mr. Santorum have been sparring for weeks over which is the more viable conservative alternative to Mr. Romney.
Mr. Santorum made the first argument with a close win in Iowa, Mr. Romney won New Hampshire and Mr. Gingrich followed by clobbering them both in South Carolina.
Mr. Romney then ran off a string of impressive victories in Florida’s primary last week and Nevada’s caucuses over the weekend.
Mr. Paul has yet to win a contest.
Mr. Gingrich had that bright spot in South Carolina after two captivating debate performances, but hasn’t been able to capitalize since.
The Gingrich camp made little noise in Tuesday’s contests, preferring to save its powder for March 6 (Super Tuesday) and the wealth of Southern states where Mr. Gingrich has polled well.
Mr. Romney won Colorado and Minnesota in his failed 2008 bid for the GOP nomination, but came in third in that year’s Missouri primary.
Earlier Tuesday, the Romney campaign sent out a memo trying to tamp down expectations of the evening’s results.
“As our campaign has said from the outset, Mitt Romney is not going to win every contest,” political director Rich Beeson said. “John McCain lost 19 states in 2008, and we expect our opponents will notch a few wins, too. But unlike the other candidates, our campaign has the resources and organization to keep winning over the long run.”
Mr. Beeson said with no delegates being awarded in Tuesday’s contests, the race will be unchanged and Mr. Romney still will have an overwhelming lead in the tally. He vowed that Mr. Romney will compete next month when Missouri holds its caucuses, which will determine delegates.
In fact, the presidential race will remain static for most of February. The next contests to award delegates loom on Feb. 28, when Arizona and Michigan hold primaries. That will be followed a week later by Super Tuesday, whose biggest prize is Ohio.
As of Tuesday, all of the candidates were vowing to remain in the race for the foreseeable future.
“I’m certainly in it all the way to the convention,” Mr. Gingrich told CNN.
• Stephen Dinan reported from Washington.
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