Following up on my post below, here’s Obama vet Jim Messina on the same topic. And he makes a point I failed to make: the real problem isn’t Biden’s age, it’s the possibility of losing because of third party gadfly campaigns. It’s happened before … MESSINA TO DEMS: CHILL OUT — Every day, it seems, there’s new fodder for Democrats looking to freak out about President JOE BIDEN’s reelection prospects: Sagging public views of the economy. Persistent voter concerns about Biden’s age. And erosion in the president’s standing among key minority groups, to name a few. The man who put the last Democratic president back into the White House — JIM MESSINA, manager of BARACK OBAMA’s 2012 reelect — is back with a reassuring message for his fellow Dems, delivered in a new 22-slide presentation exclusively obtained by Playbook: Relax. We caught up with Messina last night, and he made it clear he doesn’t see the election through rose-colored glasses. Multiple times he pointed out that (1) no matter who the Republican is, it’ll be a close election and (2) the most likely GOP nominee, DONALD TRUMP, has a strong base and can absolutely win. But the deck makes a compelling, data-driven case that the sky isn’t falling just yet — with one major caveat, which we’ll get to in a moment. “I thought it was important to say to my friends and clients and other people, let’s just take a step back and try to be really number-specific and really sort of who has what cards in their poker hand,” Messina told Playbook. “And you would just rather…