The problem for Biden is that the campaign is about to enter a phase where he cannot help being defined. A preview of this new reality came the other day. When asked if he has taken a cognitive test, Biden exploded and said, rather offensively, that the question was as silly as wondering if the black CBS reporter he was talking to had been tested for cocaine. The coming weeks will bring three major events that will convey Biden’s strengths and weaknesses before audiences of millions. He won’t be able to hide in his basement. And that may be where the fun begins.

The first event is his vice presidential announcement. Biden unintentionally backed himself into a corner by limiting his options at the start of the process, and now several of his choices would offer the Trump campaign avenues for attack. Republicans have signaled their eagerness to go after potential candidates such as Rep. Karen Bass (D., Calif.) and former national security adviser Susan Rice. Choosing Elizabeth Warren would amount to flipping the order of the ticket and allow Trump essentially to run against the Massachusetts senator rather than the former vice president. Kamala Harris seems to be the safest pick. But she’s also an uninspiring and potentially clumsy one.

The second occasion where Biden will be center stage is his convention. It’s unlikely that Milwaukee will be as chaotic as Philadelphia in 2016, especially now that neither Biden nor his running mate will be there, but one wonders if radicals want to enjoy a split-screen with the televised speeches (of either party). There is also the question of how much Barack Obama will loom over the proceedings. The Biden team and Democrats in general are convinced that more Obama is always and everywhere a good thing. But they might want to consider the possible reactions of the Obama-Trump voters mentioned above.