GRAND RAPIDS, MICH., JAN. 30 -- Vice President Bush today won a plurality of Michigan's 77 delegates to the Republican national convention, but the victory in the first state in the nation to pick delegates did not calm the battle between insurgents and the state party establishment.

In the official convention, Bush won 37 delegates, Rep. Jack Kemp (R-N.Y.) won 32 and former television evangelist Pat Robertson got eight.

Minutes after the official convention ended, Robertson flew in from Norfolk, Va., to declare the pro-Bush convention illegal before 1,000 cheering and chanting supporters attending a competing rump convention.

"Right is on our side, and we will not shrink from a struggle. In a struggle, however long it goes, we will be together as one, and we will win," Robertson said. He denounced the official convention as a "back-room deal" run by "political bosses" seeking to "control their petty little political fiefdoms."

Robertson backers, many of whom belong to evangelical Christian churches and participate in anti-abortion activities in the working-class communities around Detroit, had invested huge amounts of time and effort in the Michigan struggle. They felt cheated by what they saw as secret political deals between affluent Republican leaders and Washington-based consultants working for Bush and Kemp.

Bush, in a radio broadcast from Council Bluffs, Iowa, called the Michigan results a "big, clear win . . . . To come back like this, and to do it legally, I might add, working lawfully for victory, was very, very impressive." He described the Michigan convention as "the first really meaningful, delegate-oriented event of 1988."

At the rump convention, Robertson got 43 delegates, Kemp 21 and Bush 13. Bush and Robertson each spent more than $1 million in this contest.

Key questions facing Bush and Kemp are whether the anger directed toward them by the Christian right will carry into other states and, if either gets the GOP nomination, into a decision by Robertson supporters to sit out the general election. In the final weeks, Kemp provoked the deepest resentment among Robertson backers, who felt that Kemp's abandonment of an alliance with Robertson doomed Robertson's prospects for victory here.

Robertson campaign officials said they intend to press their claim that today's official convention was conducted illegally. Robertson will challenge the convention in the courts, where his campaign has lost all battles to date, and with the credentials committee at the national convention in New Orleans in August. Even if he eventually wins, the outcome today deprives him of the positive publicity that would have resulted from a victory here.

The results of the official convention represent a setback for Robertson, who for more than a year had been expected to win a plurality. A victory would have provided him with momentum and credibility to take into the Iowa caucuses Feb. 8. But what seemed like a sure thing just months ago collapsed into defeat after Robertson lost court fights over party rules, and then his base of support began to erode as Kemp formed an alliance with Bush.

For the past two years, the Republican Party of Michigan has been rent by the struggle between Bush and Robertson. It was the first substantial test, involving convention delegates, of the strength of the newly mobilized evangelical Christian movement within the GOP and it pitted the movement against the party establishment.

The bizarre system used to select GOP delegates here was designed to encourage increased activity within the party and to bring Michigan into the national spotlight as the first state to pick delegates.

The system succeeded in putting Michigan on the political map, but the fight has so weakened the Republican Party here that almost everyone agrees that the GOP has little chance of winning major state and congressional offices in the 1988 elections. Internal bitterness has colored every party gathering in recent months, including many of the congressional district caucuses held Friday night in preparation for the convention today.

"The Bush people remind me of the radical animals you see on campus who won't let people speak," said Debby Schlussel, a University of Michigan sophomore, as Bush supporters loudly sought to interrupt a district caucus controlled by Robertson forces. "They aren't even country club Republicans; they are animals."

"This rips the guts of the Republican Party," said Michael J. Gordon, a Bush supporter. "This convention will haunt the Republican Party for years to come."

"Michigan," said David Zachem, a Robertson tactician, "is now one of the bodies strewn on the road."

Robertson made the unscheduled appearance here shortly after noon today in an effort to take the edge off his defeat and he received extensive television coverage of his attack on the results.

The allocation of delegates in both the official convention and the rump gathering resulted from deal-making and was not bound by the one test of voters' views, which took place at an August 1986 primary election. The primary votes were only indirectly linked to the candidates.

In that primary, the Kemp, Bush and Robertson forces each sought to elect nonbound precinct delegates sympathetic to their campaigns. According to many accounts, Bush and Robertson won about 40 to 45 percent each of the 9,000 precinct delegates elected that day, and the remainder went to Kemp.

If that election had determined the distribution of delegates, Robertson and Bush would have received about 32 delegates each and Kemp about 13.

Rich Bond, Bush's deputy campaign manager, defended the process giving Robertson only eight delegates. "They didn't follow the law. They disenfranchised themselves," Bond said.

The outcome delighted Ed Rollins, Kemp campaign chairman, whose candidate went from a poor third in the August 1986 contest to a fairly close second. "We are feeling pretty good about our results -- only five votes behind Bush and closing fast," he said, smiling.

In addition to the establishment-versus-evangelical divisions characterizing the Bush-Robertson battle here, the contest had strong class and cultural overtones. While Robertson's strength was concentrated in the working-class suburbs, Bush's backing was strongest in Grand Rapids and upscale suburbs.

Throughout 1987, Robertson had been expected to win a plurality of Michigan's delegates. He had formed an alliance with Kemp and the two controlled what seemed to be a safe majority of the 9,000 precinct delegates who had the power, through a series of steps leading to today's convention, to pick the 77 national convention delegates.

Bush, however, first won a court case allowing 1,200 GOP nominees to state and local office, most of them pro-Bush, to participate as precinct delegates. Then the Bush organization successfully used party rules to gerrymander districts and gain additional strength. Robertson sought to fight these maneuvers but was again defeated in the courts. Finally, when it appeared that Bush and Robertson would win so many delegates that Kemp would finish third, Kemp abandoned Robertson's conservative coalition, ensuring the Bush victory.