Journalists have been bouncing their way through the Democratic convention, bouncing the question off each other, bouncing off the walls of this week's echo chamber.

"Will John Kerry get the bounce that Democrats hope he will at the end of this convention?" asks Fox's Carl Cameron.

"And the big question," says Claire Shipman on "Good Morning America": "what insiders call 'the bounce' in the polls the Kerry team will get."

"It's hard to get a big bounce when, like, 90 percent of the American people have already made up their mind," says MSNBC's Chris Matthews.

The B-word is inescapable in Boston, from the bars to the buzz. In the wake of Sen. John Kerry's acceptance speech Thursday night, it is being asked once again in columns and live shots, in headlines and blogs, in chat rooms and smoke-filled rooms. In today's poll-obsessed media culture, the bounce rules.

It's shorthand for "Has Kerry had a successful convention?" And that, of course, is hard to measure. How did the speeches go over? Did the carefully scripted message resonate? Will undecided voters care? It all seems so subjective. So anchors and correspondents and pundits retreat to the more comfortable realm of mathematics.

Not everyone approves. " 'Bounce,' which has replaced 'Big Mo' (Big Momentum) as the favored and most annoying cliche trotted out by lazy political reporters," writes commentator Dennis Byrne in the Chicago Tribune.

The bounce (and its first cousin, the bump) has its defenders. "It's a legitimate question because the press is obsessed with the horse race, and the bounce is a big part of how you come out of the gate for the horse race," says Tobe Berkovitz of Boston University, a commentator for the CBS station here.

Dan Kennedy, media critic for the Boston Phoenix, says bounces matter, "but like anything else in the media, it gets repeated so much that it becomes silly. . . . We all went down the road to hell by all but handing the nomination to Howard Dean by relying on poll numbers." Besides, he says, "people outside the bubble are not talking about the bounce. It's a media obsession."

Print reporters are as bounce-happy as their television colleagues.

The Los Angeles Times lays down the rule: "A good convention gives its candidates a measurable 'bounce' in public opinion. . . . A bad convention ends with no bounce at all."

"How much of a 'bounce' in the polls can the Democratic ticket expect after the balloons have fallen and the delegates shuffle back to Anywhere, USA?" asks The Washington Post.

"All this convention imagery is supposed to produce a 'bounce' in the polls," says the Philadelphia Inquirer.

Hours before Kerry's address, Newsday mixed metaphors: "A home-run speech could help Kerry win over undecided voters and create convention bounce."

How high? How does a strong bounce differ from a weak bounce, or one so feeble that the ball would be in no danger of going through an infielder's legs? That raises an equally metaphysical question: Compared with what?

The pregame bounceology began weeks ago when Matthew Dowd, President Bush's strategist, said he expected Kerry to roar out of Boston with a 15-point lead and the GOP team to catch up after Bush's New York coronation. That particular spin on the ball would make a double-digit Kerry lead seem like no big deal and anything less like a Spalding that's lost its air.

Kerry aides are avoiding the numbers game, but Democratic National Committee Chairman Terry McAuliffe allowed in one interview that Kerry should jump out to a lead of 8 to 12 percentage points.

"This is the same expectations game we played all through the primaries," says Kerry spokeswoman Stephanie Cutter. "In terms of bounce, we've already bounced."

What? How did the press corps miss that?

By running even or slightly ahead of Bush, Cutter argues, Kerry has already done what some past Democratic nominees were unable to do until after their conventions. "There's not room for an 8-to-12-point bounce because we've both consolidated our bases," she says.

But no amount of partisan handicapping can stop this bouncing ball.

CNN's Larry King: "How big a bounce do you expect after this convention?"

New Mexico Gov. Bill Richardson: "A modest bounce, maybe 5 percent."

Bob Dole: "I look for 10 to 15. A lot of people bounce around, you know. They bounce when Kerry speaks and then when Bush speaks they'll bounce again."

It's enough to make you downright dizzy.

MSNBC's Chris Matthews, above, and Carl Cameron of Fox are part of the media chorus taking the measure of the convention bounce. "In terms of bounce, we've already bounced," Kerry spokeswoman Stephanie Cutter says, citing the tightness of the race coming in.