Chris Carlson / AP Photo

Make no mistake, victories by Rick Santorum tonight in Minnesota and Missouri represent a rebuke of the " Mitt Romney will sail to the nomination" narrative. It also highlights Romney's continued struggle to win over skeptical conservative GOP voters and energize the base.

After big wins in Florida and Nevada, the conventional wisdom was that Romney had vanquished his strongest rival - Newt Gingrich - and had this nomination all but sewn up. But, the voters of Minnesota and Missouri didn't get the message. Romney came in third place in Minnesota - a state he carried in 2008.

Santorum, the former Pennsylvania senator, was boosted by the fact that social and cultural issues like Planned Parenthood, contraceptives and the Catholic Church dominated the news cycle. He was also helped by the fact that Newt Gingrich essentially conceded these contests.

So, where does it go from here? Look for Romney and the pro-Romney Super PAC to start to reload and regroup in Arizona and Michigan - the next two major contests on the docket on Feb 28. Romney is hoping his money and organizational muscle will pull him through in these states, much like money and organization helped him win Florida.

Either way, the nomination fight continues and Romney will once again have to bat away the questions about the lack of enthusiasm among GOP voters for his candidacy.

Another big loser tonight: Newt Gingrich. He's betting on a good showing on Super Tuesday, March 6th. But, for now at least, Santorum, not Newt, owns the mantle of the "conservative alternative" to Romney.