Democrats arriving here said they remained confident that Senator Obama would leave Denver at the end of the week in a strong position to defeat Senator McCain. But a convention that the Democrats had once anticipated would be a breezy celebration of Mr. Obama has turned into a more sober and consequential event.

As intense as the anticipation over Barack Obama’s choice is, it pales next to the hubbub over whether John McCain is going to tap Joe Lieberman, who was Al Gore’s running mate in 2000. This would give Lieberman a unique niche in American history — one politician who was the vice-presidential nominee for both parties. We would speak of it with awe, like that story about the two-headed turtle in Brooklyn.