MT. CLEMENS, MICH., DEC. 11 -- Frank Krajenke, Michigan president of the 700 Club and one of the new Republican bosses in Macomb County, heard that David P. Bugay was about to cast a vote damaging to the interests of Marion G. (Pat) Robertson, so he picked up the phone.

"Frank let me know they are going to make certain I'll be dead politically," recounted Bugay, an ordained Baptist minister who runs a private housing cooperative.

Krajenke, who heads both the 700 Club and the Christian Broadcasting Network in Michigan and Indiana, recalled using more temperate language. "I told him," he said, that if he tries to stay active politically, "I'll have to tell the truth about him -- that he went back on his word."

The tense confrontation between the two men is a small reflection of the explosive mix of evangelical Christianity and power politics in this state.

The combination has resulted in a battle more characteristic of Chicago's Democratic wards -- threats, job offers, backroom deals and a crescendo of bitter accusations -- than the traditionally more refined world of Republican presidential nomination contests.

The fight here escalated sharply this week as the Republican Central Committee prepared for a vote Saturday that could deal a devastating blow to the conservative alliance between Robertson and Rep. Jack Kemp (R-N.Y.).

The Kemp-Robertson coalition took over the Republican Party machinery in August 1986 and has threatened to hand Vice President Bush an embarrassing defeat Jan. 30 when Michigan becomes the first state to pick delegates to the GOP national convention.

Last Monday, however, some of Kemp's key leaders said they will abandon the conservative alliance to join forces with Bush when they vote Saturday. Defying Kemp, they have cut a deal that could give Bush a victory and Kemp a close second. Announcement of dissension in the Kemp camp converted Saturday's meeting of the 101-member central committee from what was a virtual 2-to-1 Robertson-Kemp victory into a bare-knuckles fight.

For example, L. Brooks Patterson, the Oakland County prosecutor and a leading Bush supporter, promptly called Paul Welday, Kemp's deputy Michigan campaign manager who wants to run for state representative in Oakland County.

Patterson said he told Welday employment "would be the least of his worries" if he would jump ship and give up his job with Kemp.

In addition, Patterson pointed out, if Welday cast his central committee vote with the Bush forces, he could be assured of backing from all seven major GOP elected officials in the county. Otherwise, Patterson noted, "we are just going to have sit on our hands" through the primary. Welday declined the offer.

At stake Saturday is a rules change proposed by the Kemp-Robertson alliance to bar Bush-controlled GOP county executive committees from adopting apportionment plans for selection of delegates to the state convention, which will decide the winner of Michigan's 77 national delegates Jan. 29-30.

Taking advantage of extremely liberal rules governing apportionment plans, Bush forces in the state have devised plans that minimize Robertson strength while maximizing their own. In Waterford township, for instance, the plans call for eight separate caucus units, none of them contiguous, according to an independent study, which in effect reduce Robertson's 15-to-0 delegate margin over Bush to an 8-to-7 edge.