Once all the votes are in, history may judge that the race for the 1988 Republican presidential nomination did not turn on David McKeague's early endorsement.

But for now, that's a gamble the front-rank GOP contenders seem unwilling to take.

So it's been a heady autumn for McKeague, an East Lansing lawyer whose sole claim to political prominence is that in February he became Republican chairman of Michigan's 6th Congressional District.

Last week he was ushered into a hotel suite here to get a face-to-face endorsement pitch from Vice President Bush. McKeague gamely stood his ground, telling the vice president he couldn't commit so early. Bush, he reports with relief, was "very gracious, very understanding, very accommodating" in the face of the bad news.

Two weeks earlier, McKeague had given the same demurral to Rep. Jack Kemp (R-N.Y.), who'd also arranged a private meeting. And then, a day after that, he'd offered no commitments to Sen. Robert J. Dole (R-Kan.), another courtesy caller.

That a local party activist should be in such demand 27 months before the first presidential delegate will be selected speaks volumes about the battle for the GOP nomination. It has already begun. In some quarters, it's already hand-to-hand.

The candidates all bemoan this early intensity, but none dares ignore it.

"I had hoped the whole process would wait until after the 1986 elections, but I suppose that was foolish," sighed former Senate majority leader Howard H. Baker Jr., who already hears echoes of the rhetorical question he posed when he became the first dropout of the 1980 nomination contest: Does someone have to be unemployed to wage a campaign for president?

Baker, for one, has been handsomely employed since leaving the Senate, earning an estimated seven-figure annual income from two law firm partnerships and a handful of corporate board memberships. But to preserve the option of taking another run at the White House, he has decided to throttle back his work load, hire a press secretary, form a new political action committee and accelerate his travel schedule next year -- all to match the pace of his competitors.

In addition to all this early velocity, the Republican contest has something else going for it: a distinct early shape. It may get reshuffled over and over before real-time 1988 arrives, but at least for now there's a rough consensus on who stands where.

Bush is the front-runner; Kemp the No. 1 challenger. Early in 1988, so the seers see it, these two butt heads. Maybe one man bleeds to death, maybe neither, maybe both. In the last instance, the way then opens for a Baker, a Dole, a (former Delaware Gov. Pierre) du Pont, a Sen. Bob Packwood (R-Ore.), or a who-knows-who-else to break out from the pack.

Lurking off at a tantalizing distance from the rest of the field is television evangelist Pat Robertson, the X-factor of 1988. He says he is still "praying" over whether to run, but he is getting advice and encouragement from Edward J. Rollins, the former White House political director who has gone into the consulting business. It is no accident that Robertson's Freedom Council this summer dispatched five field organizers to Michigan to teach evangelical Christians how to participate in the political process, and sent along a computer to keep track of all the names.

Michigan Republicans have gotten a corner on all this early action by setting up a multitiered delegate-selection process that begins with party precinct elections next summer. At least on the GOP side, Michigan has become the new Iowa.

Bush has studied the calendar and decided to carpet-bomb the state with endorsements. His is the classic front-runner strategy: Lock in whatever you can when it's easiest to be had.

Last week his PAC announced a 658-member state steering committee; McKeague's name may not have been on it, but not too many other Republicans were missing.

"That'll teach Kemp to tickle the elephant's" bottom, chortled Michigan's colorful national GOP committeeman, Peter Secchia, who suggested the Bush forces were galvanized to act by a surprise announcement by Kemp two weeks earlier of seven Michigan endorsements.

When Bush returns from China next week, he'll be announcing a national steering committee that should be as impressive as his Michigan haul, tapping into three sources: his own 1980 campaign organization; longtime party regulars; and big chunks of the Reagan faithful from 1980 and 1984.

Bush's lists will, of course, have built into them the familiar front-runners' curse of blessings. If things go sour for the candidate, they become a breeding ground for defectors, and "then the names are worth ten times more to us if we pick them up than they were to Bush in the first place," said John Maxwell, director of Kemp's PAC, the Campaign for Prosperity.

Technically, Bush hasn't picked up endorsements; he has merely signed on activists to help his PAC elect other Republicans to office next year. But the vice president calls his PAC "my political lifeblood," and with winks and nods he and his operatives have made it clear they want recruits for 1986 to stick around for the fun in 1988, too.

While Bush strategists understand the dangers of overdoing an "endorsement strategy," they reason it would be folly to build their candidacy on any other foundation. Bush's personality and ideology aren't of a type that attracts shock troops. He will be the safe, the known, the credentialed candidate. That's his strong hand; that's the one he will play.

The same reasoning applies to the ticklish question that confronts any vice president who wants to move up one notch: Should Bush spend the next few years fashioning a separate identity for himself in selected areas, perhaps even engaging in some small acts of distancing from administration policy where he thinks it might be politically advantageous?

"I'm too far gone . . . I'm too pregnant for that," Bush said in an interview. He added: "More than any other candidate, I am locked into how well or badly we do. If things aren't going well with the economy I would be the first to suffer."

If Bush runs in 1988 as the compleat Reagan loyalist, he risks having his differences with candidate Reagan in 1980 -- on such matters as abortion, ERA and "voodoo economics" -- thrown back at him by still skeptical conservatives. If he tries to distance himself, he gives the lie to the cheerleader's role he has carved out since taking office. It is a tightrope walk either way, but Bush says he is determined to stick with the first option.

Kemp aides, meantime, say pointedly that "we are not out beating the bushes for endorsements," in the words of spokesman John Buckley. "Ours is a campaign of ideas."

Certainly Kemp is the most ideological of the major candidates; he alone has created, in addition to the familiar campaign PAC, a tax-exempt foundation, the Fund for American Renaissance, that sponsors symposiums, publishes tracts and supports travel to popularize his monetarist economic theories and his hard-line defense stance.

Kemp will probably have the most passionate doorbell ringers of any candidate, but it does not follow that he will have the conservative franchise all to himself. The wing has gotten too big, and the center of the party moved too far right, for it to be contained in one camp.

The Rev. Jerry Falwell of the Moral Majority, for example, has already signed on with Bush, while David Keene of the American Conservative Union is consulting for Dole. If Robertson were to run, he could split a chunk of the conservative wing away from Kemp -- which may be one reason why Rollins, who plans to work for Bush in 1988, is encouraging the evangelist to do just that.

Kemp is counting on a generational appeal as well as an ideological one. The baby-boom generation will be fully into the electorate by 1988, and Kemp strategists hope they will be drawn to their man's youthful dynamism. He will present himself both as the rightful heir of Reagan ("the son of the Gipper," he was introduced recently in Michigan) and as the candidate with the vision and energy to carry Reagan's Revolution into its next phase.

Certainly Kemp's high-voltage personality is a hit on the stump; he gets 350 invitations to speak a month. This year he's already logged in 179 campaign appearances, to go with his 269 in 1984. The big question looming around Kemp is how will he stand up under the pressures and scrutiny of a presidential campaign. He has never been tested in that way before.

While Kemp is hitting the road to find his forums, Dole has been using the floor of the Senate for his. He has positioned himself as a fervent champion of deficit reduction, even to the point of crossing swords on several occasions with the White House. What Dole is building is deniability. If the economy heads south before 1988, don't blame him.

Baker is worrying about the deficits, too, and he has come up with the first blockbuster proposal of the precampaign. He is calling for a new national tax -- perhaps on energy use or retail sales -- whose revenues would be dedicated to eliminating the $2 trillion federal debt over the next 50 to 100 years. Baker knows full well what happened to the last presidential candidate who called for a tax increase, but insists: "It would be tragic if we were to let Walter Mondale's failure keep us from facing up to the most serious problem in the country."

Next year, Baker will be on the road 50 percent of the time. Du Pont, meanwhile, is already spending two-thirds of his time traveling the country for his "GOPAC," which wants to collect $5 million by 1986 for grass-roots party building. If he collects some political IOUs in the mix, well, so be it.

And then there's Packwood, who is raising money for no one but himself at a prodigious clip ($2.4 million and counting) despite the fact he has no opponent yet in sight for his 1986 senate reelection campaign. Could he be bankrolling for bigger stakes?

Stick around. This thing has only just begun.