Happy days are here again. Or so say President Bush and John Kerry (search), who paint a rosy picture of America's future when they're not pounding each other with criticisms.

"I'm optimistic about America because I believe in the people of America," Bush says in campaign commercials. Kerry does too. "We're a country of the future," the Democrat says in one of his TV ads. "We're a country of optimists. We're the can-do people."

With the presidential race even in the polls, both candidates are trying to win over voters by projecting a bright outlook, despite looming challenges in Iraq and a host of domestic woes.

"It's a bedrock principle in the United States," said Darrell West, who teaches political science at Brown University. "Americans almost always go for the optimistic candidate."

But taking the glass-is-half-full approach requires delicate balancing.

The incumbent, Bush, must couch his enthusiasm for economic growth at home with the reality of ongoing turmoil in Iraq — or risk being seen as out of touch. Kerry, too, must walk a fine line as the challenger, trying to appear positive while pointing out the deficiencies he says merit a change in leadership. But he must do it without going so negative that he gives credence to Bush's new label for him: pessimist.

Both can be done.

As the sitting president in 1984, Ronald Reagan (search) recycled his "Morning in America" campaign mantra from four years earlier into "Morning Again in America," stressing the nation was strong but could be better. Bill Clinton ran as a can-do challenger in 1992 and successfully tempered his criticism of the first President Bush while tapping into the country's upbeat, forward-looking nature.

For Bush and Kerry, the definitions of optimism are different, said Kathleen Hall Jamieson, an expert on political rhetoric at the University of Pennsylvania's Annenberg Public Policy Center.

"The president has to be more optimistic about the moment we're in," Jamieson said, "and the challenger needs to be more optimistic about where he can take you."

Both candidates have latched onto the theme. Kerry released an ad titled "Optimists" while Bush criticized Kerry in another called "Pessimism." Nearly everyday, they or their surrogates say they are optimistic about something.

Bush began his re-election campaign by telling voters he believed America was prevailing through tough times — the terrorist attacks of Sept. 11, 2001, and the economic recession. Then, the political environment turned sharply negative. His campaign simultaneously unleashed attack ads against Kerry and received a rash of difficult news out of Iraq.

Once the economy started to rebound, Bush had something to be hopeful about. He now embraces job-growth numbers — and tries to paint Kerry as a downer.

As jobs grew, Kerry argued America could do better and that Bush was not in tune with the public's concerns. The Democrat said any new jobs were low paying and proposed boosting the minimum wage. He claimed families continue to struggle and offered a plan to give parents more child care money.

Kerry noted that Bush still has "the worst jobs record of any president since Herbert Hoover" and said "the middle class has been losing."

Meanwhile, Kerry's campaign circulated a document called "Americans are too optimistic to settle for George Bush's economy" and unveiled TV ads that seek to subtly contrast policies under the Republican's administration with Kerry's own proposals — without naming Bush.

Bush swung back with the pessimist label, in effect, inoculating himself from Kerry's criticisms. The president's latest TV and radio ads list ways he says the economy is better and then accuse Kerry of talking about the Great Depression, intoning "pessimism never created a job."

At a recent speech before the National Federation of Independent Business, Bush referred to "modern-day economic pessimists," an obvious reference to Kerry. "They can find the dark cloud, but they can't see the sunshine," Bush said, "and they don't know where to take the country and they don't know where to lead."

In e-mail missives and conference calls, Bush's campaign said Kerry was on a "Pessimism and Misery Tour," and campaign manager Ken Mehlman criticized the Democrat for "talking down the economy" with "1970s rhetoric."

Republicans said Kerry simply criticizes Bush's economic policies without recognizing job growth, giving Bush legitimate reason to call Kerry a pessimist.

"It's a framework you'll see for a while," said Charlie Black, a former Republican National Committee chairman.

Democrats find it baffling that Bush is crying pessimism after spending months attacking Kerry through TV ads.

Jenny Backus, a Democratic strategist, called Bush a "Georgie-come-lately" to the notion of optimism. "Bush left open the high road for six months and John Kerry took it," Backus said.

But West, of Brown University, said Bush's new label for Kerry could hurt — if it sticks. In America, West said, "pessimism is a dirty word."