In his column in the magazine this week, national affairs correspondent John Heilemann lays out the political calculus of the upcoming Iowa caucuses, now less than a month off. One thing to watch out for is a last ditch Hail Mary from Rick Perry, a make-or-break 44-city tour through the state, where he needs to land at least in the top three come caucus day to keep his campaign (already on life support) wheezing along. Ron Paul’s historic 10 percent ceiling may be more elastic than once thought, with some “savvy Iowa political hands” predicting a second-place finish for the libertarian — an all-around Romneytastrophe scenario. And Michele Bachmann is now apparently gunning for the Romney VP slot, GOP strategists tell Heilemann, having all but given up on the whole Bachmann-Trump ticket pipe dream. As for Romney’s Mormonism, it’s shaping up to be even more of a dealbreaker among Iowa’s evangelicals than many envisioned. With the days counting down, a lot will hinge now on back-to-back debates this week: the first on ABC tonight (which Heilemann will be live-tweeting at @jheil) and the second on Fox this coming Thursday. Let the GOP Midwestern gladiatorial games begin!