Former U.S. senator Rick Santorum rejuvenated his presidential hopes on Tuesday with a shocking sweep of the three nominating contests in Colorado, Minnesota and Missouri, dealing a blow to wounded front-runner Mitt Romney.

Even though Romney still holds strong advantages in financing and organization, his campaign will now have to refocus to fight back the challenge from the surging conservative Santorum.

Backed by a wealthy “Super PAC” that pays for attack ads against rivals, Romney had excelled in major contests thus far in the race. After big wins in Nevada and Florida in the previous week, he did little campaigning in Minnesota and Missouri and had been expected to win easily in Colorado.

Until Tuesday, Santorum had won only one of the first five Republican contests in the state-by-state battle for the Republican nomination to face President Barack Obama in the November 6 election.

But on the first day of multiple nominating contests in the 2012 primary season, Santorum trounced Romney by 30 percentage points in Missouri. That vote was a non-binding primary, but has symbolic value as a measure of support in a big Midwestern state.

In Minnesota’s caucuses, Santorum won with 45 percent of the vote. But in another setback to former Massachusetts governor Romney, U.S. congressman Ron Paul was in second place with 27 percent and Romney was a distant third with 17 percent.

The race was closer in Colorado, but Romney had been expected to win easily. But Santorum won by 5 percentage points over Romney.

With eight contests to date in the Republican race – including the three on Tuesday – Santorum has now won in four states, Romney in three and former House of Representatives speaker Newt Gingrich in one.

CONTINUED at Reuters.