WASHINGTON — Hillary Clinton apparently thought that she had a killer sound bite during Thursday's debate when she ripped Barack Obama as a promoter of "change your can Xerox."
Instead, the audience booed, critics winced and once again the New York senator's attempt to demonize her rival fell flat, another illustration of how 2008, at least so far, is the year that negative campaigning just doesn't work as it once did.
"It looks like people are just burned out on that stuff," said Peter W. Schramm, the executive director of the Ashbrook Center for Public Affairs in Ohio.
In state after state, voters said they moved from Clinton to Obama — or, on the Republican side, from Mitt Romney to John McCain or Mike Huckabee — partly because they were tired of what seemed like politics as usual.
"What Hillary Clinton says just seems like dirty politics. Obama offers a very positive message," said Roshay Malone, a Milwaukee child-care business owner.
"Clinton's just too polarizing. Obama is able to inject some enthusiasm into the process," added Bryan Hale, a land surveyor from Smithsburg, Md.
Analysts warn that the campaign still could turn on negatives, should a major scandal erupt. And the rules are likely to change in the general election, which will pit candidates at largely opposite ideological poles against each other.
But for now, voters and analysts saw at least five reasons that going negative isn't a positive development for campaigns that try it:
_ Voters are excited about the candidates. "When you have two firsts — the first woman and the first African-American — there's an enormous amount of enthusiasm, and people don't want to be reminded of anything negative," said Karlyn Bowman, senior fellow at the American Enterprise Institute, a conservative research organization.
That's particularly true with Obama. Earlier this year, Clinton supporters brought up the Illinois senator's drug use as a young man and Bill Clinton had pointed criticisms of Obama in South Carolina. This week, the Clinton team hammered on how Obama used words from a speech by Massachusetts Gov. Deval Patrick, one of his campaign co-chairs.
Despite the media frenzy, Obama won Tuesday's Wisconsin primary by 17 percentage points, and Thursday he won the Democrats Abroad primary to stretch his winning streak to 11.
- Information overload. People seeking political news have more sources — updated more often — than ever, so most stories are old within hours.
"There's this steady stream of news every minute and every day. To the public, a lot of this stuff is a blur," said Kenn Venit, a television news consultant based in Hamden, Conn.
Clinton, for instance, painted herself as the victim of the "boys' club" of other candidates last fall after her rivals, all men, seemed to join one another in criticizing her vague answers at a debate. Yet the episode is barely remembered now.
The Internet and cable-TV world spent Thursday reporting on McCain's alleged relationship with a lobbyist, but by Friday the McCain news was about the Federal Election Commission warning the Arizona senator about his campaign spending.
"It's such a complex world, and there are so many influences on people," said Leo Jeffres, a professor of communication at Cleveland State University. A voter's judgment, he said, "is not as simple as it was once upon a time."
Then there's Bill Clinton, whose sexual affair with a White House intern in the Oval Office dominated the news for more than a year in the late 1990s.
So when Romney questions McCain's tax-cut votes or Clinton hurls a plagiarism charge at Obama, the public often shrugs.
"Those charges hardly stand up to the new standards of sleaze. Compare that to what Bill Clinton did," Venit said.
In that year's South Carolina primary, opponents used "push polling" to ask voters inclined to prefer McCain whether they were willing to back him if they knew he had an illegitimate black child. McCain and his wife adopted a girl from Mother Teresa's orphanage in Bangladesh.
This year, Romney tried ads and statements criticizing McCain's record — the Romney campaign said they were simply contrasting the record, not going negative — but nothing worked.
"People don't want to go there with McCain," Bowman said.
When Jimmy Carter painted Ronald Reagan as a zealot who couldn't be trusted with his finger on the nuclear button, the tactic bombed. Some voters looked at the genial Reagan and wondered what Carter was talking about.
Similarly, when Clinton goes after Obama, and he calmly responds and stays largely positive, some voters view Clinton as petty. Obama just doesn't look scary.
"I read his books and I admire him, and he stays away from negatives," said Barb Butler, a retired college administrator in Pella, Iowa.
Bob Mulholland, a California Democratic campaign consultant, found such attitudes common this year.
"The presidential race is one where voters have a lot of time to think and watch the candidates," he said. They get to know them, he said, then look for ways to confirm their feelings.
When many look at Obama, they see what Brookfield, Wis., voter Ann Sawyer saw. "Clinton is a very smart woman, and I'm glad I voted for her husband, but what Obama is doing is amazing," she said.
That's why, when Clinton brought up the plagiarism charge at Thursday's debate, it went nowhere.
As Venit put it, "There just may be a backlash this year against this kind of stuff."