New Jersey governor and almost-2012-candidate Chris Christie made headlines with his decision to endorse former Massachusetts governor Mitt Romney on Tuesday, on the eve of a presidential debate. Here’s a look at the potential impact of his endorsement.

“Mitt and ann #romney meet Karen Tumulty and Melina Mara from @washingtonpost on #econdebate floor” (A.J. Chavar/The Washington Post via Instagram)

1. Endorsements often have very little impact. Remember in 2007 when evangelical leader Pat Robertson endorsed former New York mayor Rudolph Giuliani? And the black members of Congress and state lawmakers who backed Hillary Rodham Clinton? Barack Obama easily won the black vote in 2008, while Giuliani won few evangelicals.

Polls suggest, despite the clamor in Washington and New York about Christie, that he’s not that well known or extremely popular among Republican voters. A Washington Post/ABC News poll last week suggested a majority of Republicans either didn’t have an opinion or didn’t want the New Jersey governor to run for president.

So it’s not clear how many voters will be persuaded by his endorsement.

2. In this case, the endorsement may have even less impact because of Christie’s identity. Like Romney, the New Jersey governor is a conservative, but not closely-allied with the tea party.

Many Christie backers had already decided to endorse Romney once the New Jersey governor opted against running. Christie endorsing Romney is not a surprise, like the late-Sen. Edward M. Kennedy (D-Mass.) backing Obama in 2008. It’s not like Sarah Palin endorsing Romney now.

3. Christie’s biggest influence would be among New Jersey Republicans, but the Garden State’s primary is currently scheduled for June, very late in the GOP nomination process. Nearby New York votes in April.

Why Christie’s endorsement will matter:

1.Christie’s sharp comments while endorsing Romney are likely to be remembered. His pointed criticism of Perry for embracing pastor Robert Jeffress, who made controversial comments about Mormonism, won’t help the Texas governor, who is eager to move on from that issue. And Christie tried to distance Romney from the health-care law the latter signed in Massachusetts from the federal one that conservatives hate.

2.Christie’s endorsement could push others toward Romney who would have more sway in the primary process. The endorsements of Iowa Gov. Terry Branstad or South Carolina Gov. Nikki Haley would help Romney in those early states, and those governors no doubt are aware of Christie’s decision. Also, members of Congress and major donors, who always want to back a winner, will have another reason to reconsider backing Perry or one of the other candidates.

3.Individual endorsements may have limited impact. But a group of political scientists has found that the number of endorsements by party leaders is often a strong indicator of who will win a presidential primary. (Check out the New York Times’ Nate Silver on this point and the research supporting it.)

It’s a classic chicken-versus-egg question: Do voters follow the preferences of party leaders or are party leaders anticipating the voters when deciding whom they endorse? Romney is ahead in overall endorsements from members of Congress, and Silver has a useful hierarchy of endorsements that also puts the former Massachusetts governor ahead.

The Christie endorsement helps Romney build the feeling that he is the inevitable nominee, a view I found when interviewing people in Iowa this weekend. At the same time, didn’t Hillary Clinton seem inevitable in October 2007?