If Rubio finishes worse than second, the candidate most likely to beat him is Kasich. Kasich has a 30 percent chance of finishing in first or second in our polls-plus forecast and a 23 percent chance in our polls-only forecast. Rubio’s hope as the race shifts to the South is to become the mainstream Republican candidate — the alternative to Ted Cruz’s very conservative coalition and Trump’s fandom. A Kasich second-place finish in the Granite State — and the favorable press that would come with it — could greatly complicate that path. Kasich is a better fit for the more moderate wing of the GOP than Rubio, who has a very conservative record. Kasich may not be able to win, but he can take votes away from Rubio in later states.
Even if Rubio finishes third to Cruz (who has about a 20 percent to 25 percent chance of finishing at least second, depending on which FiveThirtyEight forecast you look at), it could be spun as a major blow for Rubio. New Hampshire has a lot of moderate voters and few religious conservatives, which really limits Cruz. Ironically, Cruz could get the bump out of New Hampshire with a second-place finish that he failed to get out of Iowa with a first-place finish. In addition, Cruz is far better set up in South Carolina, which has a lot of religious conservatives. After the first three contests, Cruz could have a second-place and two first-place finishes.