The early skirmishing for the 1988 GOP presidential nomination has turned, in part, into a series of legal confrontations before the Federal Election Commission, which has the power to force alterations in basic fund-raising and spending strategies that some potential candidates are using.

Yesterday, the FEC issued an opinion specifically to former Senate majority leader Howard H. Baker Jr. (R-Tenn.) that, if applied to all potential candidates, would appear to rule out practices being used by such Baker competitors as Vice President Bush and Rep. Jack Kemp (R-N.Y.).

Anticipating such a ruling, however, Bush has asked the FEC for a separate opinion in an effort to gain blessings for the use of his $3.8 million political action committee (PAC), the Fund for America's Future, to finance steering committees, hospitality suites and the election of Michigan precinct delegates later this year.

The controversy centers around the use of "multi-candidate" PACs by many of the potential presidential candidates to finance many activities that appear to be designed to promote their chances of winning the GOP nomination.

These special PACs, whose stated purpose is to aid many candidates, such as all Republicans running in 1986, cannot be used as backdoor mechanisms to finance presidential bids and are restricted to providing help to candidates running for lower office.

The FEC specifically said Baker cannot use his PAC, the Republican Majority Fund, to pay the costs of travel, hospitality suites, the formation of steering committees and staff salaries that are linked directly to exploration of a presidential bid. These costs must be paid for by a "testing the waters" committee, which faces many more restrictions than multi-candidate committees.

Bush, noting that he has not set up a "testing the waters" committee, yesterday asked the FEC if his PAC can be used for many activities similar to those falling under the Baker opinion. Most importantly, Bush asked whether his PAC can help finance and organize candidates to run in the 1986 Michigan precinct delegate contests.

These delegates will ultimately decide the composition of the 1988 Michigan delegation to the GOP presidential convention. The FEC's ruling in the Baker case appeared to restrict sharply the scope of activities the Bush PAC can finance, but members of the FEC carefully noted that the opinion is directed only to issues raised by Baker, not by other potential candidates.