Chief strategist Matthew Dowd (search) keeps a countdown clock on his desk at President Bush's (search) re-election headquarters, telling him precisely how much time remains until Election Day — down to the second.

Sunday, the clock hits a milestone that marks the beginning of the end of the presidential campaign: 100 days left. With time running short and polls tightening, there is a rising sense of urgency.

"This race right now is dead even," Dowd said Saturday. "Everything you do and everything campaigns do, it matters in a race that could be decided by few thousand votes in a few states."

The campaign is unwrapping a home-stretch plan to ensure that Bush campaigns and advertises where it matters most, highlights his vision for a second term and energizes Republicans to vote in record numbers.

Bush is already using Air Force One for re-election trips more heavily than any predecessor, and he will ratchet up his travel significantly starting next month. White House aides say he will probably be outside Washington 28 days of 31 next month.

The trips focus heavily on the fewer than 20 states where Bush and Democrat John Kerry (search) have been fighting most fiercely.

"You don't want to send him into places where you're winning overwhelmingly or places where you don't think you can win," Dowd said.

Strategically, the Bush campaign broke the election into four quarters: Outlining the challenges the country has faced; defining Kerry and comparing the two candidates' records; offering a plan for a second term; and contrasting the Bush vision against Kerry's.

Bush has just entered the third quarter, his aides say. On Wednesday, he broadly sketched out a second-term domestic agenda that would shift focus to improving high school education and expanding access to health care.

The fourth quarter starts late next month at the Republican National Convention, when Bush is formally crowned as the nominee for a second term and starts juxtaposing his vision against Kerry's.

"Bush needs to make the case that America is better off today than it was before he took office and that we'd be better off still four years from now," said Phil Trounstine, the director of the Survey & Policy Research Institute at San Jose State University. "If he cannot make that case he's very likely to return to Crawford, Texas."

But Bush's "best hope" is easing violence in Iraq, said Trounstine, who was communications director for former California Democratic Gov. Gray Davis.

"They emphasize the war on terrorism as a permanent state of war because the best case that you can make for not changing horses midstream is when you're engaged in a war," he said.

More immediately, Bush must chisel away at the sizable "bounce" that Dowd expects Kerry will gain following the Democratic National Convention this week, part of the opposition's effort to raise expectations.

One way to do that will be a fresh barrage of advertising. Bush started July with $64 million, and must empty his bank account by the time of the GOP convention that begins Aug. 30.

He is no longer raising money for his own re-election but is routinely pulling in millions for the Republican National Committee's get-out-the-vote fund, known as Victory 2004.

The presidential debates scheduled for October could be make-or-break, Dowd said.

The Bush campaign is also making a final push to energize what it says are 850,000 volunteers around the country, an army meant to drive Bush backers to the polls.