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.

Teeter said he believed the number of voterswho were wavering was much lower, "somewhat under10 percent."

Bush professed little doubt about the outcometomorrow.

"Things are moving in our direction," he saidas he raced yesterday from Colorado to Californiato Michigan.

Dukakis, in a desperate race, noted that bothcandidates began the day in Colorado.

"For months George Bush has been following mearound on the issues. He discovered education afew months ago, he even discovered the environmenta few months ago," he said.

"This week he started following me around on mymessage, telling people he's on your side. Nowhe's following me around the country. I'll tellyou one place he's not going to follow me. He'snot following Lloyd Bentsen and me to 1600Pennsylvania Avenue."

Bentsen, the vice presidential nominee, flewfrom Illinois to Texas in a final bid to preventBush from taking his home state.

In an NBC interview, Bentsen conceded that nomatter which candidate won, he wouldn't have muchof a mandate after the election.

He also said that if he returned to the Senatein a Bush administration, he would help Bush whenhe thought it was deserved and try to block himwhen he thought the president was wrong.

Quayle, who shows up as a drag on theRepublican ticket in virtually all the polls,declined invitations to appear on networktelevision and campaigned yesterday in Virginia,one of the safest Republican states where a newpoll showed Bush with a 56-25 lead.

Dukakis used his 30-minute campaign-closingcommercial to show himself responding to questionsfrom average Americans and to trum pet thepopulist theme that has adopted in the hope ofscoring an upset tomorrow.

"Look in the mirror and ask yourself," he saysin a film clip taken from a rally. "Is George Bushon your side?