Fred Barnes‘ latest Weekly Standard article delves into the meaning of the Iowa caucus results for both Mitt Romney and former Pennsylvania Sen. Rick Santorum:

[Romney] now faces an opponent, Santorum, who can credibly claim to be an honest-to-God conservative alternative to Romney in what may now be a two-person race. Should the press go along with this, as it’s no doubt inclined to, Romney will have a tougher battle on his hands than he must have expected pre-Iowa.

Both Ron Paul, who came in third, and Newt Gingrich, who was a distant fourth, said they will take their campaigns to New Hampshire, whose first-in-the-nation primary is next Tuesday, and South Carolina with its January 21 primary. But coming out of Iowa, Santorum is the big story and the chief threat to Romney.

A one-on-one race is exactly what Romney hoped to avoid at this stage, particularly a race against a more conservative candidate with momentum from having dramatically exceeded expectations in Iowa. With three or four candidates dividing the conservative vote, Romney had an advantage that’s now gone.