Three of the four Republican presidential candidates make the Sunday talk-show rounds today, but oddly missing is Mitt Romney.  Romney has spent very little time on Sunday talk shows so far, but with Rick Santorum breaking out into a national polling lead and starting to gain double-digit momentum in Michigan and Ohio, one might think that Romney would take the opportunity to get on national TV ahead of the debate on Wednesday.  Instead, Santorum, Newt Gingrich, and Ron Paul will try to set the narrative for the Arizona debate, while John McCain tries to fill in for Romney on ABC’s This Week, which will be hosted by Jake Tapper — and that means it’s watchable.  Set your DVRs accordingly.

• ABC’s This Week: Senator John McCain, Robert Gibbs; Roundtable: George Will, DeeDee Myers, Lou Dobbs, Jonathan Karl, Clarence Page
• CBS’ Face the Nation: Rick Santorum; Roundtable: Karen Tumulty, Todd Spangler, Norah O’Donnell, John Dickerson
• CNN’s State of the Union: Ron Paul, Mitch Daniels, Michele Bachmann, former CIA Director Michael Hayden, Ambassador Ed Walker, Starbucks CEO Howard Schulz
• Fox News Sunday: Newt Gingrich, House Majority Leader Eric Cantor
• NBC’s Meet the Press: Reps. Paul Ryan and Chris Van Hollen on the budget; Roundtable: Ed Gillespie, Al Hunt, Helene Cooper, Andrea Mitchell

A couple of points to watch for in these matchups:

• On CNN, I’d expect to see Candy Crowley press Bachmann on an endorsement decision.  Crowley will certainly want to get Bachmann to weigh in on the relative conservatism of Romney, Santorum, and Gingrich, and it might produce an interesting moment, especially considering Bachmann’s influence with the Tea Party.
• John McCain will want to talk about Romney, but look for Jake Tapper to press him on Santorum’s record in the Senate, since McCain worked much more closely with Santorum than Romney.
• The Crossfire-like setup on MTP might produce a few good moments, too, especially if Ryan demands Van Hollen answer whether the Obama budget reduces spending (it doesn’t), and if it addresses long-term debt reduction (it doesn’t).  Van Hollen will try to offer a blizzard of slogans, but Ryan will have the facts and the numbers on his side.