Two months ago, I expressed my support for Rick Santorum for the Republican presidential nomination, an “endorsement” that came with some heavy qualifications, including the declaration that I would support whoever won the nomination.  Santorum’s withdrawal allows me to consider the options, but in my column today for The Week, I point out that Santorum’s success came in part from his own efforts, and in part from lingering skepticism among conservatives about Mitt Romney:

That takes nothing away from Santorum’s amazing return from electoral obscurity to top-tier contender for the nomination. As ABC’s Rick Kleincommented on Twitter, Santorum won 10 states in this contest, an incredible feat for someone who had very little financial backing until he won a surprise victory in the non-binding Iowa caucuses in January. Santorum’s relevance in April may have been the most surprising outcome in a cycle that at times seemed defined by surprises among the Republican contenders — most of them unpleasant.

Santorum’s success can be credited in no small part to his surprising strength as a candidate. He outperformed his rivals in retail politicking in Iowa and proved himself tenacious when other, more highly-regarded candidates like Tim Pawlenty and Herman Cain pulled out. Santorum also vigorously espoused his pro-life, pro-family agenda while relating both to the broader economic and fiscal concerns that drove the grassroots in the midterm elections.

However, the main subtext of Santorum’s survival was a significant and continuing level of disaffection with Mitt Romney among the conservative base. Grassroots conservatives rallied behind Santorum as the Not Romney after Newt Gingrich faded in Florida and Nevada. Santorum’s withdrawal comes after a series of losses in primaries over the last few weeks; Santorum won seven of the last 24 contests while Romney won 16 of them, with one tie for delegates in the Alaska caucuses. Santorum won only one state in the last eight contests (Louisiana).

Some of that skepticism may be evaporating, if the results in Wisconsin give any indication:

According to the exit polls from last week’s primary, Romney won almost all of the demographic categories in play. He carried a majority of Republicans (the Wisconsin primary is open to all registered voters), edged Santorum among “very conservative” voters, and won a plurality of independents. In a key indicator of grassroots response, Romney won a near-majority of Tea Party adherents (49 percent). Romney also led among Catholics, whose votes he had been regularly winning, and Protestants, where Santorum had usually performed stronger. He also won a majority among those who approve of embattled Gov. Scott Walker, which has become a cause celebre among conservative grassroots activists, and not just those in Wisconsin.

While many in the media are asking what’s next for Rick Santorum, the main question is what’s next for Republican voters in upcoming primary states.  The math, as I explain in my column, all but guarantees Romney the nomination with Santorum out of the equation.  The only potential obstacle is Newt Gingrich, who insisted yesterday that he will go all the way to Tampa and fight for delegates.  In fact, he made a plea for Santorum’s delegates as part of his statement, but there is a problem with that pitch.  Santorum has not officially withdrawn from the race, nor is he likely to do so.  He needs to retain his candidate status in order to raise funds to retire whatever campaign debt remains, and it’s likely to be considerable.  Santorum also needs to hold onto his bound delegates to negotiate a role at the convention and perhaps one in the Romney administration, if Romney wins the election.

There is a more fundamental problem with Gingrich’s plan, however, and that is a lack of credibility as a candidate at this stage.  He hasn’t won a state since Super Tuesday, and that was his nominal home state of Georgia.  In the five weeks since that time, Gingrich has won a grand total of 51 delegates and has been shut out entirely since March 13th.  He’s no longer campaigning, and as Allahpundit noted last night, the campaign bounced a check in Utah for fees connected to ballot access. It wasn’t just a momentary lapse, either:

They’ve been trying to get in contact with the Gingrich campaign since the March 29, the day they realized where the check came from. Thomas claims they’ve sent several emails, made several calls, and even sent the campaign a certified letter on Monday to tell them their check bounced. They’ve even asked the Utah Republican Party to step in and clear up the matter. So far, they haven’t heard back from the Gingrich camp.

“I get the sense that maybe they’re, perhaps, winding down over there and maybe not in the full campaign mode as maybe they were,” he said.

Gingrich’s campaign officials still have time to get his name on the ballot.

“We do need payment before we will certify Gingrich’s name for the ballot,” Thomas said. “We gave them the deadline of April 20th to get that into our office.”

Laura Ingraham mentioned this on her show today, and the Gingrich campaign responded that the bounced check was caused by “a technical error.”  The technical problem appears to be that they didn’t have the cash to cover the check, and that they don’t have anyone to respond to the problem.  Needless to say, that’s not a campaign that is ready to become an alternative to the Romney campaign, no matter how much one likes the candidate.

It’s time for everyone to acknowledge reality.  Mitt Romney is the nominee.  He won the nomination through hard work and good organization, but his competition forced him to improve his performance along the way.  The sooner we put fantasies of brokered conventions and one-on-one debates between Republicans — which will only serve as media fodder to attack the GOP — the better we will begin to prepare for the real goal of this process, which is to make Barack Obama a one-term President.  With that goal in mind, I plan to caucus for Romney in the upcoming CD and state Republican conventions in Minnesota and work to unite the party behind its nominee.  However, I also plan to support candidates in the House and Senate that will ensure that a President Romney governs as a conservative, as Donald Devine advises post-Santorum.

Let’s win an election, folks.

Update: Santorum super-PAC funder Foster Friess switches to Romney.  Don’t be surprised if Sheldon Adelson makes the same move soon.