It is all but a dead cinch now that Mitt Romney will be the Republican nominee for president this year, not because he accrued the delegates he needs — he hasn’t — but because the campaigns of his two closest rivals have imploded.

Newt Gingrich’s sugar daddy Sheldon Adelson, owner of the Venetian and Sands casinos in Las Vegas, recently announced he was pulling the plug on the Gingrich campaign. Gingrich is “at the end of his line,” Adelson said in informal remarks at a Jewish Federation of North America event in one of his casinos.

Rick Santorum inadvertently revealed that he knows his campaign is over — a revelation he has not shared with his donors or supporters — in an interview on Pat Robertson’s televangelical “news” network. Asked if he would be willing to be Romney’s running mate, Santorum said, “Of course. I mean, look. I would do in this race as I always say, this is the most important race in our country’s history. I’m going to do everything I can.”

Wrong answer. The correct answer would have been, “Fortunately, I’ll never have to make that decision, because I am going to be the nominee.” Thanks for playing.

The likelihood Romney would choose Santorum as his running mate is zilch — and not just because Santorum lost his last Senate race in Pennsylvania by double digits or because the Obama campaign would have a field day producing ads showing Romney’s running mate shaking an Etch-a-Sketch, describing Romney as “uniquely disqualified,” a “well-oiled weather vane,” “bland and boring” and a “bully.”

But that’s just one reason the Romney campaign won’t choose Santorum. The other reason is that Rick Santorum is a Catholic.

In the Republican primaries and caucuses so far, Romney has lost nearly every county that is dominated by his party’s evangelical base. He lost statewide in Alabama, Georgia, Iowa, Kansas, Louisiana, Mississippi, Missouri, Oklahoma, South Carolina and Tennessee. He won Florida overall but lost in the predominantly Christianist north-central counties. The only Southern state Romney has won is Virginia, but that was a fluke because neither Santorum nor Gingrich were on the ballot.

In nearly every other instance, evangelicals have voted against Romney and for Santorum or Gingrich, both of whom are Catholics. And while this may seem to indicate a preference for Catholics over Mormons among evangelicals, it is not entirely clear that these notoriously low-info voters are even aware that Santorum and Gingrich are, in fact, Catholics.

Gingrich was not a Catholic during his years of his climb to the top as speaker of the House — his second longtime mistress and now third wife Callista made him convert recently. As for Santorum, a Pew Poll in mid-March found that only about a third of Republican and Republican-leaning voters were aware that Santorum is a Catholic. About a third of evangelical voters said they thought he was one of them.

There is no doubt that Romney will carry most of the states where evangelicals hold sway. But there are three Southern swing states that Obama won in 2008 where Romney could have trouble in 2012. Polling shows he is currently well behind Pres. Obama in Virginia, and it is a distinct possibility that both Florida and North Carolina could be in play this fall.

If the GOP nominates a Mormon and a Catholic this year it could risk alienating “values voters,” a great many of whom believe that Mormonism is a satanic cult and that the Catholic Church is represented by the Whore of Babylon in Revelation. Depressing turnout among evangelicals in Virginia, Florida and North Carolina could lead to a disastrous outcome for Romney in a close election.

The problem for the Republicans is that excluding Catholics would eliminate not only Santorum and Gingrich, but every candidate on the Beltway media’s short list as well, including Florida Sen. Marco Rubio, New Jersey Gov. Chris Christie, Virginia Gov. Bob “Vaginal Probe” McDonnell, New Mexico Gov. Susana Martinez, former Florida Gov. Jeb Bush and former New York City Mayor Rudolph Giuliani.

It gets worse. With the blowback from John McCain’s disastrous decision to go for a “game changer” and nominate Sarah Palin for vice president in 2008 still causing headaches for the GOP, it’s fair to assume that team Romney won’t go for an out-of-the-box choice this time around — meaning no women, persons of color or unknowns. That would exclude Palin as well as retiring Texas Sen. Kay Bailey Hutchinson, South Carolina Gov. Nikki Haley, Louisiana Gov. Bobby Jindal, former RNC Chair Michael Steele and Florida tea party Rep. Allen West.

To play it safe, the Romney campaign has to choose a Southern straight (sorry Lindsey!) white male with tea party bona fides and a nationwide ID.

And here the pickin’s get slim. Texas Gov. Rick Perry disqualified himself during his short-lived foray into the primaries by proving that the joke about him — that he is George Bush without the brains — is true. And former Mississippi Gov. Haley Barbour sidelined himself a few weeks before he left office this year by pardoning dozens of people convicted of serious crimes, including rape, robbery and murder. Florida Gov. Rick Scott probably has the name ID and bona fides, but he won election by the thinnest of margins in 2010 and has become deeply unpopular ever since.

There are no other well-known Southern governors, but if Romney’s goal is to assuage concerns among his party’s mostly Southern base, he should probably avoid choosing Yankees. If so, that eliminates Ohio Gov. John Kasich and Wisconsin Gov. Scott Walker, both of whom are racing Florida’s Gov. Scott to the bottom in approval polling, as well as Indiana Gov. Mitch Daniels, whose baggage includes marital difficulties and a stint as George W. Bush’s budget czar.

All of this narrows Romney’s choices down to a few Southern senators, among whom only a few have the sort of national name recognition the campaign needs: Jim DeMint, the tea party apparatchik from South Carolina; Lamar Alexander, a moderate from Tennessee; Richard Shelby, a sad sack with zero charisma from Alabama; and Jefferson Beauregard Sessions, another Alabamian whose baggage includes sketchy views on race, including once stating that he liked the Ku Klux Klan until he found out they smoked pot. Former Senate majority leaders Trent Lott of Mississippi and Bill Frist of Tennessee also have problems. Lott has worked exclusively as a lobbyist since he left office, and Frist’s reputation for catching and killing cats early in his medical career would be a constant reminder of Romney’s horrifying abuse of his family’s Irish setter.

Among that group of finalists, one stands out: Sen. Jim DeMint, a Presbyterian who is not only a tea party boss but also a vicious political knifeman, and, like Romney, an easy and practiced liar, all of which makes him well-qualified to be the Romney campaign’s designated attack dog in the fall.

Romney-DeMint 2012. It fairly rolls off the tongue.