Reacting to expressions of strong voter sympathy, the Montgomery County Republican Central Committee has endorsed a proposed tax-cutting amendment to the county charter despite the outspoken reservations of the party's candidate for county executive and half its County Council candidates.

Republican county executive candidate Richmond M. Keeney reacted to the GOP committee's action yesterday by saying that his own more conservative tax abatement program could be "married" to the charter amendment if voters approve the amendment by referendum in the November election.

"I think it is a positive indication that the Republican Party supports a reduction in the tax load," Keeney said yesterday. "I prefer my approach, but if TRIM (the acronym for Tax Relief in Montgomery that has been given the amendment) is approved, I will make every effort to implement it and am, in fact, spending a good deal of time now determining how it will affect the government.

The 19-member Republican central committee's overwhelming endorsement of TRIM Tuesday night, with two members dissenting and at least four not voting, turned the local version of California's tax-cutting Proposition 13 initiative into a partisan political issue.

The Democratic Central Committee is likely to oppose TRIM, which will appear on the ballot as Question E, when it meets in two weeks, according to preliminary indications.

A Republican-Democratic split on the issue would have particular significance as Republicans devote the most energy in recent campaigns to winning seats on the now all-Democratic council and keeping the executive's post in GOP hands.

The county Republican organization now plans a mailing to all households favoring approval of the TRIM amendment, which Keeney and at least three GOP council candidates have opposed as "irresponsible."

Like Keeney, the three GOP council candidates opposed to TRIM - Jackie Simon, Taft Holland and Barbara Bailey - yesterday downplayed the political influence of the central committee's action on their campaigns. They said that because they hold the longstanding Republican posture that taxes must be cut and government waste curtailed, their philosophies and the tax-cutting movement are not inconsistent.

Two other Republican council candidates - Malcolm Lawrence and Bob Brennan - are supporters of TRIM. Barrie Ciliberti could not be reached to clarify his position, and Richard L. Bogley was hospitalized last week after a serious heart attack and was unavailable for comment.

State Sen. Charles Gilchrist, the Democratic county executive candidate, and six of the seven Democratic council candidates - Elizabeth Scull, Neal Potter, Rugh Spector, Esther Gelman and Michael Gudis - oppose TRIM. Only Democrat Rose Crenca, an officer in the Taxpayers League which sponsors TRIM, has expressed support for it.

The major despute among Republicans at the central committee debate was over how deep budget cuts would be. The Taxpayers' League has contended that TRIM could roll back real estate property taxes from $2.00 to $2.25 per $100 of assessed value, slicing $25 million from the budget. Without TRIM, the 1980 budget is estimated to be $562 million.

County Attorney Richard McKernon has said that the rollback should also apply to special tax levies, causing a $90 million drop in revenues.

Several Republicans praised the central committee because, as one put it, "there is no sidestepping on this issue any longer. You're either for it or "against it."

"Keeney's proposal is a very good one, but unfortunately it isn't on the ballot," said Pat O'Hanlon, Republican Party chairman. "We don't feel these positions are mutually exclusive."

Keeney's "tax abatement" plan would roll back the property tax rate cuts to $2.12 per $100 of assessed value, but would spread the cuts over four years.