Mitt Romney's dominant position in the Republican presidential race was dealt a punishing blow Tuesday when rival Rick Santorum handed him defeats in Minnesota, Missouri and Colorado.

Romney entered Tuesday’s contests having won three states and lost two. He has now lost five states – including every state in the Midwest and South that has held a primary contest. His loss was especially stinging in Colorado, where he won with 60 percent in 2008 and was expected to coast to victory.

Santorum’s sweep of all three states also lent new credibility to questions about whether Romney’s appeal among conservatives is strong enough to win him the nomination. It also gives Santorum the air of momentum heading into a three-week lull until the next two primary contests on Feb. 28 in Michigan and Arizona.

Romney has been poised to easily win both of those states; Now, all bets are off.

The former Massachusetts governor congratulated Santorum on his Tuesday wins in an address to supporters in Colorado, conceding that Santorum had a “good night,” but quickly pivoted to attacks on the easier target of President Obama.

“We will take our message of liberty and prosperity to every corner of the country,” Romney said. “And when this primary season is over, we will stand united to defeat Barack ObamaBarack Hussein ObamaOvernight Energy: Dems ask Pruitt to justify first-class travel | Obama EPA chief says reg rollback won't stand | Ex-adviser expects Trump to eventually rejoin Paris accord Overnight Regulation: Trump to take steps to ban bump stocks | Trump eases rules on insurance sold outside of ObamaCare | FCC to officially rescind net neutrality Thursday | Obama EPA chief: Reg rollback won't stand Ex-US ambassador: Mueller is the one who is tough on Russia MORE and restore the values that have made America the greatest nation on earth.”

Romney’s campaign is well-funded and has already organized a solid ground game in states weeks and months out, while his rivals have been limited to focusing on states voting in the immediate future. But Santorum’s triple win on Tuesday was expected to spark an influx of donations that could help him close the gap, and earn him a renewed look from the media.

Anticipating a defeat in at least one of the three contests, Romney’s campaign earlier on Tuesday downplayed expectations and pointed out that none of the contests held were binding on delegates.

But those efforts were unlikely to be enough to quell speculation that he is losing steam just as his rivals are discovering renewed strength.

Romney had been leading in the polls in Colorado and campaigned heavily there, even while Santorum was focused on Missouri, where the race was less crowded because Newt Gingrich was not on the ballot. Romney also had reason to believe he would do well in Minnesota, which he won in the 2008 GOP primary.