After weeks of former Massachusetts Gov. Mitt Romney hoping that New Jersey Gov. Chris Christie would keep the intrigue alive before re-finalizing his decision not to run for president, it’s Texas Gov. Rick Perry’s turn to do the hoping.

For Perry it’s a wish that Christie re-opens the door to a White House run and gives moderate Massachuser Romney a taste of what the Texan has had to contend with for his two months in the race: a divided base. Christie is said to be preparing a mid-week announcement and Romney needs a definite “no.”

The only threat to Romney’s core support so far has been the candidacy of former Utah Gov. Jon Huntsman. But while Huntsman looked good on the pages of Politico, it turned out that there was little interest in the Republican electorate for a second moderate Mormon candidate. Romney has had to do little to respond to Huntsman, even as the Obama appointee increasingly focuses his dwindling resources on upsetting his rival in New Hampshire.

If Christie runs, though, it would be a calamity for Romney.

While it is fashionable to paint the Republicans as a party of extremists, the truth is that the GOP is variegated. Southern conservative evangelicals dominate the party, but Romney has proven that there is a considerable group that prefers a more moderate candidate, even one from the deep-blue confines of New England.

It wouldn’t normally be enough to win the GOP nomination, but Romney has been advantaged by the ongoing divisions inside the Republican right. While Perry has emerged as a late contender, his weak performance in the FOX News/Google debate has left the door open to other conservative candidates, both cultural and fiscal. There’s been Rep. Ron Paul, Rep. Michele Bachmann and former Sen. Rick Santorum, and now there’s businessman Herman Cain and former House Speaker Newt Gingrich.

While Perry has been defending himself from a sustained attack from the right, Romney has mostly gone untouched as the GOP base settles scores. Both Santorum and Cain are 2008 Romney backers who are likely to eventually fall in behind the current frontrunner, and purists Bachmann and Paul are unlikely to line up with anyone. Only eternal optimist Gingrich seems prone to back whomever emerges as his party’s nominee.

Northeastern moderate Christie, though, would be a tough dose for Romney to take. Christie has tremendous support inside the Republican establishment, which is more moderate than the rank and file to begin with. Christie’s support of some gun control measures, embrace of civil unions for gay couples, decision to minimize abortion as an issue and appointing of a Muslim activist to New Jersey’s Superior Court are all pluses for Republicans who believe the party has gone too far right and needs to moderate in order to defeat Obama next year.

While Perry has managed to hold on to top-tier status despite his poor debate showing, Romney has little room for error. Romney’s strategy depends on winning early primaries in more moderate New Hampshire and Nevada to answer probable Perry wins in Iowa and South Carolina. Romney then needs to win in Florida before settling in for a long haul in a nomination process the Steele-era Republican National Committee decided to make as long as possible.

If Christie were to run, many moderate GOPers who have increasingly come to accept Romney as their standard bearer would jump ship. While Christie might not be able to upset Romney in New Hampshire, where Romney keeps a summer home, or in heavily Mormon Nevada, the New Jerseyian would cut into Romney’s support in Florida and in the all-important stealth primary for establishment support. One can see how the David Frum set would leap for Christie, cutting into a core constituency for Romney.

Christie’s presidential hand-wringing has been helpful to Romney since it has allowed his campaign to continue to argue that the GOP field is in flux. Christie’s Hamlet play has kept some big-money donors on the sidelines and forestalled the moment at which Republicans come to accept their fate and choose between two imperfect frontrunners. Since Christie is mostly known for his tough talk and not his moderate politics, he’s been a net negative to Perry as a quasi candidate.

But if Christie were to decide to run, it would be only bad news for Romney. Christie could actually deliver what Huntsman threatened: a centrist rivalry. Romney’s greatest strength so far has been his implacable support in the center. He has not increased his share of the electorate, but has emerged as the frontrunner by holding fast to a quarter of the GOP. If Christie were to divide that base, it would mean big trouble.

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