SOME FUTURE chronicler of these things may record that Judge George Boucher, a trial court judge in Grand Rapids, and Dick Posthumus, a state legislator from Lowell, Mich., in actions taken last week, delivered the presidency to George Bush. We emphasize the may: Judge Boucher's decision last Friday could be overruled, and Mr. Posthumus and his allies may not have enough votes to swing a rules decision toward the Bush forces and away from the Robertson-Kemp coalition at next Saturday's party state central committee meeting in Lansing -- and even if it all does work out in the vice president's favor, he could kick the prize away.

But for the moment, anyhow, things are going Mr. Bush's way in what will be the first contest in the nation. Republican precinct delegates elected in August 1986 will meet Jan. 14 in 83 county conventions to elect delegates to the state convention Jan. 29: there Michigan's 77 Republican national delegates will be chosen. Since the Robertson-Kemp coalition won a clear majority at last February's state convention, it seemed likely to elect most of the national convention delegates, leaving Mr. Bush a poor third. Now the coalition has at least partly broken down, and Bush managers are sniffing possible victory.

And they could just win if higher courts agree with Judge Boucher. He ruled that a state law giving some 1,200 local and party officials -- most of them Bush backers -- votes in the county conventions takes precedence over the Robertson-Kemp party rule that says they don't have votes. That ruling seems to go against a Supreme Court ruling that state laws don't govern national party conventions, but the two situations are not identical, and it's possible Judge Boucher will be upheld on appeal.

Mr. Bush's other boost came Monday when Mr. Posthumus and other Kemp backers said they would oppose a Robertson-Kemp move to pass a party rule freezing (with two exceptions) the districts from which state convention delegates are elected to the lines used last February. If the state party votes Mr. Bush's way, county parties can change the districts -- as they have been doing in several counties where Bush forces are in the majority. That would give Mr. Bush more state convention votes and a real chance at first place.

Both sides of these arguments proclaim that the other is unjust, but it is awfully hard to see a right and wrong here. Each campaign is trying to maximize its votes in the old-politics system that Michigan Republicans have revived for 1988. The stakes are high. Assume a first-in-the-nation win for Mr. Bush, assume it will give him a boost in Iowa, where Bob Dole now leads him in polls, and you can easily write a scenario showing George Bush wrapping up the nomination early. Assume a Robertson-Kemp win, with a strong Dole showing in Iowa, and you have the ingredients for a long and wide-open race. The Michigan result is still in doubt. What is clear is that it is a little wacky for the Republican presidential nomination to hang -- quite possibly -- on the decision of a Grand Rapids judge and a Lowell, Mich., state senato