The Democratic National Convention will bring wide weeklong exposure to John F. Kerry and John Edwards, with a dozen networks on hand and thousands of print reporters. But 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?

Kerry's people say not much. President Bush's camp says a lot.

This is, of course, all about managing perceptions and expectations. Democrats are dampening hopes, lest the convention fail to produce a big bump among voters. Republicans, meanwhile, are trying to raise the bar to make any post-convention surge seem disappointing.

Matthew Dowd, chief strategist for Bush's reelection campaign, said earlier this month that the Democrats should have a lead of more than 15 percentage points coming out of the convention. (Most polls show Kerry with a slight edge now.) Dowd based that figure on the average amount of support challengers have picked up after announcing their vice presidential pick and after the convention in every presidential race since 1976. Bush campaign officials stuck by Dowd's number last week.

In a memo on the subject, Dowd cited a bullish comment made by Democratic National Committee Chairman Terry McAuliffe on CBS's "Face the Nation" on July 4: "I think you're going to see Senator Kerry anywhere from 8 to 12 points up" when the convention ends.

Not gonna happen, Democrats say.

Mark Mellman, Kerry's pollster, says that Kerry has already gotten his bounce -- he's consolidated Democratic support (there aren't many "swing" voters left to convince), which has left him in a far stronger position than most challengers have been going into their conventions. Mellman points out that since 1956, incumbent presidents have held an average lead of 16 points in preconvention polls, which means Kerry is ahead of the typical benchmark.

In a memo replying to Dowd, Mellman suggests that the pressure is actually on Bush. Only three sitting presidents over the past 50 years have been behind in the polls after the challenger's convention, he says. And all three (George H.W. Bush, Jimmy Carter and Gerald R. Ford) lost.

As for McAuliffe and his "Face the Nation" prediction? The DNC chairman wasn't talking about it last week.

Tuned In or Tuned Out

Preliminary indications are that voters are very interested in the Democratic convention. And preliminary indications are that they aren't.

In a survey released Wednesday, Marist College found that 65 percent of those asked planned to watch some or "a great deal" of the proceedings in Boston. But the folks at the Kennedy School of Government at Harvard, in a poll released the same day, reported that only 31 percent of the people in their survey said the same thing.

This is social science?

Even the two men who conducted the polls can't reconcile the huge disparity, except to suggest the other guy's poll was somehow flawed. Both polls asked roughly the same question, both were conducted around the same time (mid-July), and both used nationwide samples. "Without seeing their data, I can't really explain it," said Lee Miringhoff of Marist.

Thomas E. Patterson of the Kennedy School says historical patterns suggest his poll will be closer to the mark. Ratings for the conventions have been falling for decades. (In 1976, the average household watched more than 11 hours of convention coverage; by 2000, the figure was down to two hours, an all-time low.)

It's not clear that the 2004 conventions will set a new low, however. Both the Marist and Kennedy School polls agree that interest in the general election is heightened this year, which bodes well for convention viewing.

Even so, the commercial broadcast networks' decision to telecast just three hours each from Boston (down from five hours each in 2000) is a bad sign for the Democrats. Convention coverage on these networks (ABC, CBS and NBC) picks up millions of "casual" viewers that cable networks (C-SPAN, CNN, Fox News, etc.) never do, in part because many households don't have cable and because the big networks are almost always the highest-rated channels, Patterson says.

Here's how important broadcast TV coverage is: During the 2000 conventions, the audience ranged from 15 million to 27 million households when the broadcast networks carried coverage. With cable-only coverage, the audience never exceeded 10 million.

Patterson thinks the networks should carry more of the convention to fulfill their officially mandated "public service" requirements. He thinks the networks' argument against more coverage -- that declining ratings don't justify it -- is a self-fulfilling one. "They are as much leading" the viewership decline as following it, he says.

To back that up, he points to statistics from Nielsen Media Research that show that the networks have cut their convention coverage hours at a far faster clip than the corresponding decline in the audience. Observes Kennedy, "There's a market out there, but if you starve it, it shrinks."

Democrats seem ready to rally around a Kerry-Edwards ticket. The Democratic National Committee chairman predicted an 8- to 12-point bump in the polls after the nomination is accepted. Historically, candidates have fared better after conventions.