Why Marco Rubio’s endorsement matters to Mitt Romney

Florida Sen. Marco Rubio’s decision to formally endorse Mitt Romney’s presidential bid on Wednesday night doesn’t matter all that much in and of itself.

In this Feb. 9, 2012, file photo, Sen. Marco Rubio, R-Fla., addresses the Conservative Political Action Conference in Washington. (AP Photo/J. Scott Applewhite, File)After all, the Florida Republican presidential primary was almost two months ago and everyone already knows that Rubio will be one of the major contenders to be vice president when Romney makes his pick later this summer. (He is ranked #1 in our vice presidential Line.)

But that doesn’t mean that Rubio’s endorsement is meaningless — particularly in light of the events over the past few weeks.

In just the last 9 days — since Romney won the Illinois primary — he has been endorsed by former Florida governor Jeb Bush and former President George H.W. Bush while leading tea party Senator Jim DeMint has said kind things about him and Freedomworks, a tea-party aligned group, has dropped its opposition to him as the nominee.

Add Rubio’s support into that mix and it’s clear that the slew of endorsements for Romney in recent days have done something for the Massachusetts governor that winning primaries had not: Make clear he is the Republican presidential nominee.

Think about it. Romney’s victories in Florida, Michigan, Ohio and Illinois all came after polling suggesting he was either trailing or tied with former Pennsylvania senator Rick Santorum or former House Speaker Newt Gingrich.

Romney’s come-from-behind victories in each state did little to rally the activist base of the party behind him despite the fact that with each win he was building a delegate edge over his rivals that made him insurmountable — or close to it.

After each victory, Romney and his political team would plead their case to reporters; You said he needed to win, he won, they would argue. What more does he need to do?

But, it never worked. Until the Bushes, Rubio and DeMint stepped in, that is. The diverse elements of the GOP came together in that quartet of endorsements — DeMint and Rubio from the tea party wing, the Bushes from the establishment wing — to make clear to anyone who still had doubts that while it had been a good race, the race was now over.

To be sure, Romney would have almost certainly preferred more full-throated endorsements from Jeb Bush, who endorsed via press release, and Rubio, who endorsed on Sean Hannity’s Fox News Channel show.

But, the strength (or lack thereof) of the endorsements proved to be less important than the fact that Romney won them at all.

Assuming he wins in Wisconsin on Tuesday, Romney will effectively end the race — even if Santorum continues on all the way through his home state of Pennsylvania, which is set to vote on April 24.

The key to Romney’s closing out of the nomination fight, however, won’t be his margin in Wisconsin or any other state going forward. It will be the endorsements he won over the past nine days.