Vice President George Bush and Gov. Michael S. Dukakis both laid claim yesterday to precious, last-minute momentum in their campaign marathon, the vice president declaring the tide was "moving in our direction" and the combative underdog insisting he was "rocking and rolling" to an election victory tomorrow.

The political equivalent of a nuclear exchange occurred on television, where the Republicans and Democrats spent millions of dollars in advertising for the waning hours of the campaign. The two candidates bought time for 30-minute commercials on all three major networks for election eve tonight.

Although national polls pointed to a victory by GOP nominee Bush, both candidates battled the clock and physical exhaustion in a final drive to snare undecided voters and nail down a claim to the presidency.

NBC News said Bush led nationally by five percentage points and that one of every five voters was undecided or might switch allegiance.

"There ain't no stopping us now unless we stop ourselves," the vice president said at a breakfast rally in Colorado Springs, Colo.

"We can't turn the White House over to the people who claim to be on our side but who left the country on its back," Bush said.

Countered Dukakis, also beginning his day in Colorado: "He's slipping and sliding, we're rocking and rolling." he sought to raise fears over the possibility that Bush--if elected--might put vice presidential running mate Dan Quayle in charge of the White House crisis management team.

"Gives you the chills, doesn't it?" Dukakis asked. "Think about it--the Cuban missile crisis, with Dan Quayle incharge."

Democrats voiced confidence they would retainor perhaps widen their majorities in the House andSenate in tomorrow's balloting, and they gotlittle dissent from Republicans on that score.

One of the tightest Senate races is in Florida,where a late-hour poll showed a virtual dead heatbetween Democratic Rep. Buddy MacKay andRepublican Rep. Connie Mack for the seat beingvacated by Democratic Sen. Lawton Chiles.

Democrats also hoped for modest gains among the12 gubernatorial races on the ballot.

It is the costliest campaign in Americanhistory, and just one piece of it, a series ofCalifornia ballot initiatives, had a price tag ofmore than $100 million.

A series of state polls provided a picture ofseveral close races. One poll gave Bush a 17-pointlead in Texas, with its 29 electoral votes. ButDukakis was reported gaining on Bush in the latestsurvey in Colorado and holding an eight-point leadin Iowa.

NBC News said its nationwide survey completedSaturday night showed the vice president with alead of 48 percent to 43 percent--an improvementover two weeks ago. The network said a very high21 percent of the voters are "undecided or maystill change their minds."

Bush pollster Robert Teeter, interviewed onNBC-TV's "Meet the Press," rejected complaintsthat the vice president had run a nasty campaignand said private GOP surveys showed Bush leadingby a bigger margin than reported by the network.