As with Rick Perry and Newt Gingrich, when Santorum first got a lot of attention in February, voters gave him the benefit of the doubt and assumed he had no weaknesses. Santorum surged and defeated Romney in Minnesota, Missouri, and Colorado. His numbers rose nationally, and Santorum began out-polling Romney in Michigan by a large margin. Here's how the voters saw things:
Romney vs. Santorum
Romney and Santorum are equally electable.
Santorum is much more conservative than Romney.
Result: Santorum wins.
The voters' views of both attributes should be unsurprising. While Romney was known as a "Massachusetts moderate" and "flip-flopper," Santorum's conservatism had not been vetted. On the electability measure, Santorum again benefited from a lack of vetting, while Romney had also just come off a damaging gaffe in which he suggested he didn't care about the poor. Romney's electability took a hit for the second time this season (the other being when voters worried he had something to hide in his tax returns). If anything, some voters probably thought Santorum was more electable than Romney.
But, as with other surging candidates, Santorum's rise has prompted more media scrutiny. Romney's attack machine has directed its fire toward Santorum, rightly assuming Gingrich is no longer a real threat. In Michigan, Romney's attack ads have primarily been directed at making voters question Santorum's conservatism.
Will voters buy the idea that Romney is more conservative than Santorum? No. But it's not necessary: Romney only needs to close the gap. Even before Perry's debate gaffes made voters view him as unelectable, Perry was hurt when his conservatism was questioned. Making him appear only somewhat more conservative than Romney did a lot of damage, because it undermined the whole point of the Perry candidacy, which was to be very conservative.
As with Perry, attacks against Santorum's conservatism will be effective, because voters are unaware of Santorum's weaknesses on that attribute. At the debate on February 22nd, Santorum's imperfections were exploited. But at the end of the day, voters will still view Santorum as being at least somewhat more conservative than Romney. Santorum simply appears more genuine.
The battle between Romney and Santorum will come down to electability. Having closed the gap on conservatism, voters will prefer Romney if they believe he is more electable than Santorum. Perry's drop in perceived electability occurred when he self-destructed in the debates. Romney's attacks against Gingrich, in which he painted Gingrich as a flake with ethics problems, were also devastating.
But Romney has not yet rolled out similar attacks against Santorum's electability. Instead, the only electability issues raised against Santorum thus far have come from the media, which have highlighted Santorum's extreme social views, such as opposition to contraception. It's a tricky matter, because Romney does not want to attack Santorum from the left. When Gingrich and Perry attacked Romney from the left by criticizing Bain Capital, it backfired. Still, Romney is currently relying on the media to do some of the work for him. It's never a good idea for a candidate to rely too much on the media.
Prior to the February 22nd debate, Romney and Santorum were roughly tied in Michigan polls. Here's where they stood before the debate:
Romney vs. Santorum
Romney is marginally more electable than Santorum.
Santorum is somewhat more conservative than Romney.
Result: Inconclusive.
If Romney is able to drag Santorum's perceived conservatism down close to his own level (he'll never drag him all the way down) then Romney will have a slight edge. If Santorum's electability comes into question--particularly if he seems too extreme on religious/social issues--then Romney will have a big advantage.
