The second presidential debate, in Nashville on Tuesday night, provided voters more comparative visuals on Sen. John McCain and Sen. Barack Obama, broke little if any new ground on policy and certainly occasioned no knockout punches.

Anyone who has been paying attention to the candidates this year has a reasonably decent idea of their positions, both in terms of general outlook and in specifics on key issues. There thus remained two reasons to watch the most recent debate.

First, the crashing and burning of the U.S. and world economies is relatively recent, as is the $700 billion rescue attempt put forth by the Bush administration and approved by Congress. The candidates' role in contributing to the current problem and in identifying a road out of the swamp are thus relevant to the choice of the next president.

The other reason to watch was the thought that something might happen in it that would define the campaign. One candidate, for instance, might lose his temper. One of them might step verbally beyond the usual bromides and say something horrendous that would perhaps determine the outcome of his campaign and the election. For better or worse, none of that happened.

On the policy side, the unsurprising differences did generally emerge. Mr. McCain showed himself more literate on the economy than his pre-campaign confessions of ignorance on that subject might have suggested. Mr. Obama showed himself to be more comfortable with foreign affairs and national security-related subjects than his opponent's claims suggested in the first debate.

Both provided useful, capsulated versions of their positions on some of the complex issues in the campaign, including health-care measures and foreign energy dependence.

As to stylistic impressions that viewers carried away, Mr. McCain looked old. Addressing a crowd of people whom he has never seen before repeatedly as "my friends" and coarsely referring to Mr. Obama as "that one" probably didn't help either. Whether the voter sees Mr. McCain's persona as worn-out or seasoned depends to some extent on the eye of the beholder.

Mr. Obama appeared on his toes, comfortable in his role and good-humored in the face of Mr. McCain's near-rudeness. His treatment of the "invade Pakistan" question was less than elegant, but so was Mr. McCain's.

There is one more debate to go, next Wednesday at Hofstra University in New York. The first two haven't moved the needle much in the campaign, but then, given the inherent superficiality of the format, they shouldn't.