But does Santorum's hard-won popularity with religious fundamentalists in the American Heartland make it now a two-man race with Romney - the delegate leader and still the overwhelming choice of the GOP establishment?
Or does the Pennsylvanian's lack of money and organization - and the fact that last night's victories won't translate to many delegates (zero in Missouri, where the vote was a "beauty contest") - mean that last night was just a right-wing temper tantrum on Romney's road to the nomination?
Those who know Santorum best aren't sure, but they said yesterday's success was a tribute to the tenacity of a candidate who was working the megachurches of suburban Minneapolis on Super Bowl Sunday while Romney took the day off to watch football.
"He believes - and he believes in himself more than anybody else believes in him," said Jon Delano, the politics editor at Pittsburgh's KDKA, who has watched Santorum since his upset win of a congressional seat in 1990. "That's fundamentally Rick Santorum and why he's been so successful.
Here are some major takeaways from Santorum's second surge:
The new anti-Mitt? The hardcore GOP base - older, white, evangelical, and sympathetic to the tea-party movement - continues to look for an alternative to the former Massachusetts governor, and so last night's Santorum wins could spell big trouble for the other "not-Romney," Newt Gingrich.
Since winning the South Carolina primary, the former House speaker has had a horrendous two weeks and was nearly invisible yesterday. The Georgian is pinning his hopes on a last stand in more-conservative Southern states that vote on "Super Tuesday" March 6, but Santorum's momentum may make it impossible for Gingrich to get his groove back.
