George Bush, ready to claim the Republican presidential nomination, decided to make a whirlwind trip to the GOP convention city Monday to dictate the platform he wants in his race against Democrat Michael Dukakis.

The vice president's unusual decision to address the platform committee, which is putting together themes for the 1988 campaign, is another indication Bush is ready to take command of the Republican Party and put his personal stamp on the convention that opens a week from Monday night.In the past several days, Bush has signaled a new stage in his run for the presidency, naming former Treasury James Baker to manage his campaign, cutting off all but the mandatory duties of the vice presidency, moving into campaign headquarters and trying to emerge from President Reagan's shadow.

Bush was scheduled to spend only a few hours in New Orleans, arriving from his summer home on the Maine coast to address the platform committee and then speak to Republican National Committee volunteers.

Bush was expected to generally endorse the conservative 1980 and 1984 platforms on which Reagan and he rolled to victory but also possibly to ask for the addition of GOP policy on such increasingly prominent issues as child care and the environment.

A New York Times-CBS News poll released Sunday pointed out how crucial next week's Republican National Convention is to Bush.

The survey showed Bush trailing Dukakis 50 percent to 33 percent, 17 points compared to 8 points after the Democrats' highly successful national convention in July. The poll's margin of error was 3 percentage points.

More significantly, the telephone poll of 941 registered voters taken last week found that Democrats rated higher than Republicans in helping the middle class, which includes many of the Reagan Democrats who could hold the key to the election.

Democrats also fared better when voters were asked which party would improve education and reduce the federal deficit. Although a majority said Republicans would maintain a stronger defense, only 37 percent had confidence in Bush's ability to deal wisely with a difficult international situation - a bare 2 points higher than Dukakis, the governor of Massachusetts.

Republicans hope their convention will give Bush the same kind of "bump" in the polls Dukakis received from the Democrats' gathering and cut the size of the gap to 10 percent or less.

Baker, who resigned Friday as treasury secretary to take over the Bush campaign, believes the convention will show a more independent Bush and turn the election into a close race.

"He will be seen in an entirely different light once he is the party's nominee . . . a bit more free to speak his own mind and to speak out on issues distinct and different from the administration," Baker said Sunday on NBC's "Meet the Press."

Saying Bush has been hurt by his loyalty to Reagan and the "inherent problem" of running as an incumbent vice president, Baker said Bush has "separated himself in a number of respects from the administration and begun to define his own individual persona. That will continue to an even greater extent coming out of the convention."

Baker said the election will be decided by the differences between Bush and Dukakis.

"The American people need to reflect upon whether they want a future that will build on the peace and prosperity which we have seen over the past two terms of the administration or whether they want to run the risk of losing that peace and prosperity," Baker said. "That's the real choice in this election, and that's the choice Vice President Bush will put to the American people."