Democrat Michael Dukakis lashed at front-running George Bush as man with "no convictions, no ideas and no plans" yesterday and blamed Republican policies for last year's stock market plunge. Bush tried to contain supporters' enthusiasm over polls showing him building a large lead.

"We're not going to lighten up," the Republican presidential nominee said while campaigning in Missouri. "No votes can be taken for granted and I'm not taking any votes for granted. I will continue to campaign as an underdog."

There was no question who was the real underdog--Dukakis. But he drew enthusiastic crowds as he campaigned through Michigan with aides battling the growing perception that Bush had taken an insurmountable lead with just three weeks until the election.

Dukakis' running mate Lloyd Bentsen delivered a strongly worded response to the Republicans, accusing Bush of running "one of the most outrageous displays of negative campaigning ever seen in the history of national politics."

The Massachusetts governor sharpened his language as he focused on economic issues and portrayed Bush as the candidate of the wealthy.

"George Bush cares about he people on Easy Street," Dukakis said. "I care about the people on Main Street. He's on their side. I'm on your side."

"Duke, Duke, Duke," chanted the crowds.

Dukakis also brought up the huge stock-market drop that occurred one year ago today.

"The trade deficit had soared," he said. "Republican policies of borrow and spend and borrow and spend had done the damage."

He pledged to eliminate the $150 billion trade deficit in four years by reducing the budget deficit, increasing foreign trade, investing in education and putting more emphasis on research. He said Bush wouldn't talk about his plans.

"He's got the flags and balloons, but no convictions, no ideas and no plans," Dukakis said.

The Democrat's aides disputed an NBC-Wall Street Journal poll showing Bush with a 17-point lead, his largest of the campaign. They pointed instead to other polls indicating about half that margin.

Bush, trying to avoid overconfidence, campaigned in Fulton, Mo., and invoked the memory of Winston Churchill at the Westminster College where Churchill delivered his 1946 "iron curtain" speech warning of Soviet expansionism in Eastern Europe.

Bush said the demarcation between East and West is now "a rusting curtain." He said that if elected he would be wary of Soviet intentions, despite what he called more enlightened leadership under Mikhail Gorbachev.

"Now is not the time to abandon realism about what moves the Soviet Union," Bush said.

The Bush campaign began airing tough new television commercials that ridicule Dukakis and say he has "opposed virtually every defense system we developed."

The ad uses videotape of the helmeted Dukakis in the turret of an M-1 tank, a ride the Democrat took last month in an attempt to show toughness on defense issues--but which critics said made him look silly.

Dukakis spokeswoman Lorraine Voles called thead "more distortions from the Bush campaign."

The Dukakis campaign dispatched dozens ofworkers from his national headquarters in Bostoninto the field, along with more than 1300 newvolunteers from Washington. The campaign said 60percent of the headquarters staff was beingassigned to campaign duties in target states.

Among the other volunteers are students,congressional aides and Washington attorneystaking leaves for the final three weeks of thecampaign.

Public polls ranged from bad to worse forDukakis, though his aides pointed to what theysaid was a new Harris poll putting the gap at 9points. Barbara Winokur, a spokeswoman for LouisHarris & Associates, said Harris would release apoll today but declined to comment on its resultsin advance.

Two other surveys found Bush leads of aboutthat size. One, of 1002 registered voters polledSaturday through Monday, put the race at 49-39;another, of 1201 likely voters Friday throughMonday, put it at 49-40.

Both were ongoing tracking polls--in which thenewest day's result is added to several days beingcovered and the oldest day's is dropped--done byKRCCommunications Research in Cambridge, Mass.They had three point error margins.

Republican vice presidential candidate DanQuayle traveled by bus caravan through smallIllinois towns, accompanied by Gov. JamesThompson. Quayle said he felt "a specialobligation...to help George Bush define the needsof a new generation of Americans, theirchallenges, their responses."

"With George Bush you get experience," the41-year-old Quayle said. "With me you get thefuture, the future of America."

Bentsen, in Los Angeles, denounced Bush'scampaign attacks on Dukakis as "an utterly viciousonslaught of distortion and characterassassination." He said the Democrats have "been alittle too flabbergasted sometimes to make aproper response."

"They don't seem to mind if what they say isuntrue," he said. "They don't seem to worry ifit's misleading. They don't seem to care that whatthey do is downright mean. If it sounds good, sayit. If it sells, package it. If it looks good,nominate it.