Ezra Klein takes up the subject of Biden’s age and makes a good point, with which I have to agree. One reason for my hesitance to declare Biden too old to run in 2024 is that I thought his age was a problem in 2020, too. Everything people say about his age now was true then. He was halting on the stump. He fumbled words and phrases. But I’d argue the problem was worse then. The linguistic stumbles were paired with an aging outlook. Biden reminisced fondly about his relationships with segregationist senators and seemed to think the bipartisanship of yesteryear was recoverable in the present. He wielded his connection to Barack Obama as both spear and shield — it was the case for his candidacy and his all-purpose defense against attacks. But Biden wasn’t Obama and the Senate of the 1970s is long gone. Biden’s problem in 2020, in other words, wasn’t just his age. It was that he seemed stuck in the past. But Biden proved — and keeps proving — doubters like me wrong. He won the Democratic primary, even though voters had no shortage of fresher faces to choose from. He won the general election handily, despite Donald Trump’s vaunted talents as an insult comic and a social media force. Voters seemed perfectly happy with Biden as a communicator. Campaigns are a (lengthy) sprint. But governing is a marathon. Last year, as Biden’s agenda languished, I found myself worried about his vigor again. Perhaps a younger, more energetic Biden would’ve…