It's seminar season, time for experts and unemployed candidates to talk about overhauling the way Americans nominate and elect their presidents. They'll get scant encouragement from President Bush.

Bush, who won once and lost once under the current system, said he will "play by the rules until some better ones come along.""I'm not going to spend any time trying to redo it," he said in an interview before his inauguration.

Campaigns grow longer and more costly every time, presidential primary elections multiply, and for a while after each election, there is talk of change in the name of reform. It's been that way since the Democrats began changing the system nearly 20 years ago. That changed the process for Republicans, too, because the primary election laws enacted by state legislatures usually cover both sides.

So far, efforts at change have only made campaigns more complex, more expensive and more time-consuming.

Long before Bush has been in the White House a year, prospective challengers will be making their first moves toward the 1992 campaign, most of which will have to do with raising money. Step one these days is to set up a political action committee to bankroll preliminary operations.

All told, there were 38 presidential primary elections in 1988. On a single night, Super Tuesday, 20 states - a dozen of them in the South - chose nominating delegates by primary or caucus.

Democratic re-reformers tried to put more political savvy in their nominating process by guaranteeing party elders and officeholders seats at the Democratic National Convention. But that was scaled back at last summer's convention under pressure from Jesse Jackson, who got almost no support from those ex-officio delegates.

That was part of a peacemaking package with Gov. Michael Dukakis, the Democratic nominee against Bush, and it illustrates the reality the reformers can't alter. The nominating system in both parties bends to accommodate the candidates who master it to gain power.

Southern Democrats devised the Super Tuesday notion, which was supposed to give their more conservative constituencies an early and influential voice in the contest for the 1988 Democratic nomination. It sent the party no clear signal - the path was left open for Dukakis. But it was a turning point for the Republicans as Bush came close to a sweep.

Bush said early this month that "the regional concept was . . . something new this time . . . and it proved to be a tremendous boon for me."

He said other regions will start looking at alliances that would cluster their primaries to increase their influence. "The Western states some day are going to get together and say, `Why should we be left out all the time? Why shouldn't we get in there and be up front?' "

That's occurred to some other regions, too. New England made a stab at it, but wound up as an adjunct to Super Tuesday, in part because New Hampshire was not about to give up its premier primary to enter into a group.

There are other proposals for restricting primaries to certain dates so there would be a limited number of election days during the primary season, and by a combination of date and region so that candidates wouldn't spend so much time traipsing between distant campaign states.

Bush doubts the revisionists will get far. His skepticism is founded on experience. It happens every fourth year. Bush said he'd seen it coming - "Everybody's going to go up to Harvard . . . and try to figure out what's wrong with the system.

"I don't think you're going to redesign it," he said.

And he certainly isn't going to try. "Why should I go out and say Iowa's a lousy idea?" he asked. "I'm here because of Iowa. . . . Not Iowa in '88, Iowa in '80."

In 1980, Bush upset an absentee Ronald Reagan in the Iowa precinct caucuses, first event on the presidential campaign calendar. That vaulted him out of the field and ultimately led to his nomination for vice president. In 1988, Iowa was his most severe setback - Bush ran third. But as vice president he was able to come back quickly.

"You want to get that broad perspective," he said, looking back. That perspective comes most readily to winners.