President Ronald Reagan will give his official farewell tonight to the Republicans who have loved him so well the past eight years, and in his speech before the National Republican Convention he'll pass the mantle of Republican leadership to Vice President George Bush.

This past week Reagan presented Bush a gavel, a symbolic gesture of the passing of the reins. Monday night he will closely tie Bush to the successes of the Reagan years and say the work isn't finished - Bush must be elected president.Reagan arrived Sunday evening and addressed a huge rally. He said in referring to the Democratic nominee, Michael Dukakis, he will use "the L word" for the rest of the campaign. "For he is liberal, liberal, liberal," Reagan told the rally.

But Monday will be the president's day in the sun.

After a tribute to first lady Nancy Reagan and a 20-minute video about the Reagans, delegates inside the huge Superdome will scream their appreciation as Reagan addresses the 40,000 loyalists during prime- time TV.

Republican National Committee press aides say the president will praise Bush to the rafters of the huge building, whipping the delegates up to go out and work for Bush in their home states.

Bush arrives Tuesday morning, coming up the Mississippi River on a boat to a welcome at the famous Jackson Square.

Bush has decided not to announce his vice presidential candidate until Thursday, keeping the 2,227 delegates and thousands of news reporters guessing as long as possible - a move he hopes will keep interest up during the first three days of the convention.

The New York Times reports that the final six candidates under consideration are Sen. Robert Dole, who was the most serious challenger to Bush early in the primary system; his wife, former Transportation Secretary Elizabeth Dole; Sen. Dan Quayle, R-Indiana; Sen. Pete Domenici, R-N.M.; Sen. Alan Simpson, R-Wyo.; and Rep. Jack Kemp, R-N.Y., who was also an early presidential candidate. However, Simpson, saying he has alienated too many sacred cows during his years in the Senate, took himself out of consideration Sunday.

Those six have been given speaking slots before various sessions of the convention, and their reception will be watched, Bush aides say.

Two of the final five will speak Monday night before Reagan does - Elizabeth Dole and Kemp, both scheduled to speak between 7 and 8 p.m. MDT.

Kemp told the press Monday morning he will stress the main theme of Monday night's speeches - how Reagan and the Republicans have whipped inflation, unemployment, high mortage rates, long gasoline station lines "and a sense of depression" during the past eight years.

Speakers have been warned to stick to their allotted time - or they may start disappearing. The space behind the speaker's podium sits on an elevator, and long-winded speakers could be lowered out of sight, said National Party Chairman Frank Fahrenkopf Jr.

That was apparently inspired by a speech during the Democratic convention in Atlanta by Arkansas Gov. Bill Clinton that went 31 minutes too long on prime-time TV while Clinton ignored red warning lights.

The convention actually started Monday morning at 9 MDT with a variety of welcoming speeches, committee reports and speeches by one-time presidential candidates Alexander Haig and Pete DuPont.

While Bush previews the possible ticket-mates, Sen. Gordon Humphrey, R-N.H., still leads a conservative effort, with threats of a November boycott, aimed at forcing Bush to pick a conservative vice president, like Kemp.

Sen. Dole toured the Superdome Sunday and told reporters that he is just as conservative as Humphrey and that no conservatives should threaten a vote boycott just because their person isn't picked for the ticket.

The Democrats used their national exposure last month to bash Bush, apparently successfully considering a bump in the political polls for Dukakis. (That bounce led to a 17-point lead right after the Democratic convention, a lead that in a new ABC News poll had dropped to zero. Other recent national polls show a 7-point lead for Dukakis.)

So Republicans plan some Dukakis bashing the next four days.

That started Sunday morning when, after a Republican Governors' Association brunch, a number of governors said Dukakis' so-called Massachusetts Miracle is a sham.

Republican governors know how to balance budgets, several said, and they don't leave their states in a financial mess that needs a large tax increase, as Dukakis just imposed in Massachusetts.

Utah Gov. Norm Bangerter was one to criticize Dukakis. "We can't go the ultra-liberal direction of Dukakis and Jesse Jackson," he said.

Former Education Secretary T.H. Bell, a Utah delegate, said he would be meeting with GOP education officials to discuss how Dukakis has been no friend of education.

"We can't let the people be fooled by Dukakis' campaign and the Democrats' platform," added Bangerter.

That platform will be much discussed this coming week. Bush said he wanted a specific platform and he got it.

The inch-thick document is three times longer than the Democratic platform, which, by design, is a broad philosophical work.

The Republicans' 30,000-word platform takes 125 positions not even mentioned by the Democrats, Republican platform committee members said. Few of the GOP delegates will likely read their whole platform, but party workers are preparing summaries and will also provide "objective" comparisons between the two platforms, party press officials said.