Mitt Romney won a valuable seal of approval Thursday night when Kentucky Sen. Rand Paul endorsed him for president – even though Paul’s father, Ron Paul, has not formally withdrawn from the presidential race.

The younger Paul’s support could be a boon to Romney as he tries to rally one of the more elusive parts of the GOP coalition: the youthful, disaffected, libertarian-leaning activists who powered Ron Paul’s presidential run.

But the upside goes both ways on this one: while Paul is a helpful validator for Romney, endorsing Romney also gives Paul a level of mainstream credibility he lacked during his 2010 Senate campaign. It shows he’s willing to be a team player when it counts, and puts him on the safe side of any speculation over a third-party libertarian push.

And that could be crucially important or Paul if he decides to seek the White House himself in 2016 or beyond – as any number of operatives believe he hopes to do.

“Rand’s endorsement of GOP nominee Mitt Romney clearly shows that in spite of those who try to marginalize him, he has keen set of political instincts and is very much aware that a successful national run will require more than just his father’s loyal following,” said one Republican strategist close to Paul-world.

So if Romney wins, Paul will be in a position to act as a voice of accountability on the right without being accused of sour grapes, or of having worked to undermine Romney from the start.

And if Romney were to lose, Paul would be able to tell the party in 2016 that whatever insurgent instincts he may have, he got on board with an establishment nominee at a moment when it mattered.

(Source: Politico)