LANSING, MICH., NOV. 20 -- Supporters of Vice President Bush today sharply escalated the battle for Michigan's 77 GOP delegates, raising the strong possibility that the selection process here will degenerate into a series of competing county and state conventions, clouding the significance of what was to be the first choosing of presidential delegates in 1988.

Bush supporters angrily accused opposition leaders today of lying and using "fascist" tactics by proposing another change in delegate-selection rules.

The exchange was prompted by a decision by leaders of the campaigns of Marion G. (Pat) Robertson and Rep. Jack Kemp (R-N.Y.) to break a deal made last April with the Bush campaign to forgo any further rules changes.

In what is now widely viewed as a political disaster, the once-strong Michigan GOP has been torn apart by a plan designed to make Michigan the first state in the nation to pick delegates to the Republican national convention.

The state GOP created a process that began in August 1986, when Republican voters elected 9,000 "precinct delegates" ultimately empowered to pick the 1988 national convention delegates. But every step in the complex process since then has been marked by intensified hostilities between the Bush campaign and an alliance of Robertson and Kemp supporters who have taken over the state central committee.

The possibility of both sides holding competing rump conventions means that no matter which candidate gets a plurality of Michigan's national delegates, his opponents have the potential to so confuse events on Jan. 29 and 30, when the delegates are to be chosen, that it will be very difficult for anyone to determine the winners and losers.

Today, the hostilities reached new heights as Oakland County Prosecutor L. Brooks Patterson, a Bush supporter, at a news conference called state Sen. Richard Posthumus, a Kemp backer, "a liar" who he "would not trust . . . to watch my trash on collection day."

Separately, Peter Secchia, GOP national committeeman and a Bush supporter, said in an interview: "This is not the first time I've been surprised by these fascist tactics." Secchia said the Kemp-Robertson maneuvers remind him of the story of a citizen of Nazi Germany who said, "First they came for the Jews and nobody said anything, and then they came for the Catholics and nobody said anything, and then they came for me and it was too late."

Dick Minard, who is running the Kemp campaign here, countered that the Bush forces "are bad losers and they are resorting to gutter language. I won't take myself down to the gutter with them."

Minard and other members of the Robertson-Kemp coalition said they intend to stick by plans to call a Dec. 12 meeting of the state central committee to adopt a set of rules that most camps here agree would doom a sudden resurgence of Bush strength.

If, however, the central committee goes through with the decison, Patterson and state Sen. John Engler vowed to hold county delegate-selection conventions in defiance of the state party, starting a confrontation that would not be resolved until the New Orleans national convention, when, most likely, the Michigan dispute would have become irrelevant.

The current conflict grows out of the unexpected resurgence of Bush's chances in the state. After the 1986 primary selection of the precinct delegates and the subsequent takeover of the GOP by the Robertson-Kemp alliance, many officials here believed that Bush faced the prospect of near-certain defeat despite the backing of most of the party's traditional elite and his 1980 victory, when he decisively beat Ronald Reagan in the primary.

Since then, however, Bush forces have been working quietly at the one level of the party where they have, in many cases, retained control of the party structure: the county executive committees. Under existing party rules, these committees have extraordinary powers to decide how the 9,000 precinct delegates will choose 1,805 state convention delegates. These 1,805 delegates, in turn, will name the 77 national convention delegates at a Jan. 29-30 gathering in Grand Rapids.

In those counties where Bush holds a majority of the precinct delegates, they have, when possible, chosen winner-take-all systems to guarantee 100 percent support for Bush. In a number of counties where Kemp and Robertson have a majority of precinct delegates, Bush-controlled executive committees have drawn up what aides call "extremely creative apportionment plans" maximizing their own votes, and diluting the strength of the Kemp-Robertson alliance. The Kemp-Robertson forces used similar tactics early this year to take over the state GOP.