The end is near for Rick Santorum. That doesn’t mean, though, that it’s time for Mitt Romney to start celebrating. Yes, Romney won Wisconsin Tuesday night, and has a near-lock on the eventual nomination. But claims that he is beginning to seal the deal with party conservatives are premature. A look at Wisconsin exit polls shows that he is still struggling among right-wing voters. That has clear implications for the type of general election campaign Romney can run—and the kind of vice-presidential candidate he’ll eventually have to pick.

What did we learn from the Wisconsin primary? The first exit poll reports seemed to project a 7-point margin for Romney, and an impressive showing among very right-wing voters. “Evangelicals, tea party supporters, those supporting ‘traditional values’ and people calling themselves ‘very conservative’ went Romney’s way, exit polls showed,” CNN’s Peter Hamby reported in an early analysis. The final exits, though, told a different story, one more consistent with Romney’s narrow margin of victory of only 4 points: Santorum enjoyed his accustomed win among evangelicals, and there was a tie between the two candidates among “very conservative” voters. Santorum also won among the more than half of primary voters who say they attend church weekly, and among rural voters. Yes, Romney made strides among all the traditionally pro-Santorum demographic groups, and won some, but breakthrough is too strong a word.

Romney had better hope Santorum is out of the race or out of money by May, when almost every state voting has demographics significantly less favorable to the frontrunner than Wisconsin’s. The issue isn’t whether Romney will win the nomination—proportional allocation of delegates in the most troublesome May states, along with a decisive group of pro-Romney primaries in June, ensure that he will. But his continuing struggle among the most conservative segments of the GOP may mean he has to spend far more time courting them than he’d prefer.

There are other signs of conservative intransigence on the horizon. Some analysts noted that 28 percent of Wisconsin primary voters thought Rick Santorum was “too conservative.” Less mentioned was that 23 percent said he was “not conservative enough.” It’s unclear exactly how much overlap that group had with the 44 percent of Wisconsin voters who said the same thing of Romney. But it is obvious that much of the GOP base believes the field of primary candidates was never conservative enough to begin with—a belief encouraged by Mitt Romney’s super PACs, which tried to counteract the skepticism towards their candidate by mounting relentless attacks on the conservative credentials of Santorum (and earlier, on Newt Gingrich). In state after state, Romney was winning votes from hardcore conservatives, not because he had persuaded them of his conservative credentials, but because he had persuaded them to train their ideological ire against the competition. Stoking the grievances of the party in this way may have been an instrumentally useful tactic to gain the nomination, but it has also made it that much more difficult to unify and energize the base behind his general election campaign.

In any case, the long-awaited pivot to a general election message, already complicated by his communication director’s “Etch-a-Sketch” gaffe, could be delayed considerably. Once the primaries finally end, conservatives may shift from resisting Mitt by voting for Santorum to making shrill demands on Romney-as-nominee.