Within the inner circle of the Reagan campaign and on the floor of the Republican National Convention, George Bush is almost home as Ronald Reagan's running mate.

"Gov. Reagan is 90 percent of the way toward choosing Bush as his running mate," one Reagan intimate said today.

Another well-placed Reagan source said that "Bush was the only political choice who makes sense -- and Gov. Reagan is known for making sensible choices."

On the convention floor, Louisiana delegation chairman John Cade Jr. said that it was his feeling "that Bush is pretty well decided on and the rest is just window dressing. I can't believe the man [Reagan] has come to Detroit today and doesn't know who the vice presidential nominee is."

But while Cade favors Bush, his delegation voted 2 to 1 in support of Rep. Jack F. Kemp of New York for vice president, and the Virginia, Oklahoma, Arizona and Washington delegations also lined up behind Kemp as battle lines were drawn in the convention.

But conservative Idaho, led by Sen. James A. McClure, voted narrowly for Bush as its first choice over Kemp, and Alabama split between the two prospective vice presidential choices.

Among the delegates there seemed little sentiment for the three other prospective running mates supposedly on Reagan's list -- Indiana Sen. Richard G. Lugar, former secretary of defense Donald H. Rumsfeld and Tennessee Sen. Howard H. Baker Jr.

An NBC survey of more than 77 percent of the delegates found Bush leading in preferences with 47 percent (731 delegates), and Kemp second with 35 percent (537 delegates).

Baker was third and Lugar, whose speech on the convention floor today failed to generate any conspicuous enthusiasm, was a distant fourth.

"The best thing that happened to Lugar was that Reagan was flying to Detroit at the time and didn't see it," said one Reagan source.

Rumsfeld, who spoke tonight, also seemed to be generating relatively little backing. Casper Weinberger, once a key Reagan aide in California, said he would be "surprised" to see Rumsfeld the nominee, adding: "He's a pretty abrasive fellow and he's no admirer" of the former California governor. p

Reagan has given no public clues to his decision about his running mate, which he will announce Thursday morning. But in a series of meetings in the next two days, he will hear a refrain in which the major chords will be struck for Bush, the former Texas congressman and ex-ambassador to the United Nations who proved Reagan's most persistent adversary in the long GOP primary campaign.

The most important voice likely to be raised for Bush is that of Gerald Ford, who meets with Reagan privately Tuesday afternoon. Sources close to the former president said he will recommend Bush as his first choice for the No. 2 spot.

This is the way one Reagan aide described the case for Bush:

"The voters are going to look right through Reagan at the vice presidential candidate. [Because of Reagan's age, 69], they are going to realize that if they vote for Reagan, they're voting for two presidential candidates, not one. You can't make someone presidential in a six-week campaign; there is not time to change his image. There are four Republicans who are presidential -- [John B.] Connally, Ford, Baker and Bush.

"Connally has too many negatives and Ford won't do it . . . Baker is acceptable but you're giving up something if you take him -- a skilled leader in the Senate.

"Also, Baker did not get votes in the states he ran in. With Bush, you've got a guy who carried the states Reagan has to win, Michigan and Pennsylvania, and who ran strong in Ohio, New Jersey and Texas. He's been campaigning; you can't start out cold on the campaign trail and be good . . . Taking an unknown would be a disaster."

The only real obstacle to Bush at this point seems to be a lingering belief that he is not personally synchronzied with Reagan.

"It's a class thing," said one Reagan intimate. "George is very good at asking people to support him for president. He's not as good, one to one, telling Reagan the same thing for vice president."

And in the Bush camp, there was a concern expressed by one supporter that Reagan thought Bush "arrogant, capable of upstaging Ron in certain circles, mostly monied, mostly East Coast."

Bush's strategists were determined to prevent any public demonstration that could be misconstrued in this way.

While Bush met with his delegates and urged them enthusiastically to support Reagan, his supporters called off a scheduled demonstration in which buttons reading "Reagan-Bush, Unify the Party" were to be distributed.

"We don't want to be pressuring Gov. Reagan," said a leading Bush backer, who added that the ultimate decision was likely to come from Reagan's impressions of Bush in a face-to-face meeting.

It is not certain at this point that such a meeting will take place, but there are many close to Reagan and Bush who think it will.

"We have time on the schedule for him to do that," said Reagan chief of staff Ed Meese. "It's up to him [Reagan] if he wants to."

There was some sentiment at the convention that the Republican platform plank that retreats from 40 years of support for the Equal Rights Amendment may help lead Reagan to Bush, an ERA supporter.

"George Bush was pretty much out of it when I arrived here last week for the platform committee," said Rep. Margaret Heckler of Massachusetts. "But the ERA issue has come out so deeply I now think they are looking at George in a different light."

One darkhouse possibility, Michigan Rep. Guy Vander Jagt, who will deliver the keynote address to the convention Tuesday, offered a unique recommendation for his designation as Reagan's running mate.

"I may be the least objectionable of all the contenders," he said.

Vander Jagt emerged from a meeting with Reagan campaign manager William J. Casey and said he thought he was very much in the running.

One other candidate whose name is scheduled to be put into nomination as a favorite son by the North Carolina delegation is Sen. Jesse Helms, a leader of the far right forces here.

Helms has made it known that he particularly wants to block the nomination of Bush.