The most serious Democrat challenging President Joe Biden for the party’s 2024 nomination for president just got a harsh reality check on his social media. Dean Phillips, who has said he’s running for president because he thinks Biden is one of the few Democrats who would lose to Trump despite the fact that the lawmaker has voted with Biden’s policies the vast majority of the time, has made age a central tenet of his campaign. He has said he thinks it’s time for Biden to pass the torch to a new generation. With Biden’s age likely on his mind, Phillips on Christmas day took to social media to p…