It was not a confession that political candidates usually like to make, but Richmond M. (Max) Keeney seemed unperturbed as he explained that philosophically, he differed only marginally from his two Republican primary opponents for Montgomery County executive.

"We are really saying pretty much the same things," Keeney said, leaning back in a chair in his small, jumbled campaign suite. "Taxes is an issue, but there we just see different answers to the same objective.

Then, prompted by his campaign manager, Keeney delivered what he and most of his party supporters believe is the overwhelming argument for his nomination for the leading position on the Montgomery County Republican ticket.

"The real difference" between the primary candidates, Keeney said, "is experience in government. I have as much background as anyone around. I know the issues inside and out. My opponents have just not had that kind of experience."

In the absence of issues or strong voter interest in the Republican primary for county executive, Keeney, 48, a former County Council member who has served on the Montgomery County Planning Board since 1975, expects to win on the sheer weight of his political experience - and the name-recognition it entails.

It's not that his political career has been particulary smooth. After winning a seat on the council in 1966, Keeney often angered party leaders by opposing the positions of other Republican members of the council. In 1970, he was unseated by Democrat Neal Potter, and subsequently suffered an embarrassing defeat in the 1974 Montgomery school board race, finishing last in a general election field of eight.

But as Keeney argued in a letter last month to county precinct chairmen, the warlords of primary races, "Voters are disenchanted with people who have little, if any, practical knowledge of the job . . . my opponents . . . would be novices in county government . . . We must nominate a person "who is really electable in November."

Keeney feels he has the same potential to appeal to Democratic voters as James P. Gleason, the retiring Republican executive who has won the only two executive elections, since the post was created in 1970. Keeney says he decided to run when Gleason announced his retirement.

Keeney's argument about his experience has worked with many Republican workers, even those who would normally support Keeney's more conservative - though lesser known - opponents, Albert Ceccone and Gerald Warren.

"I'm conservative myself," said one member of the Montgomery Republican Central Committee, "but I have to give Keeney the edge. The background that he has has given him a platform all this year."

"What you have to understand about Keeney," said the county's Republican member of Congress, Newton I. Steers, "is that he has done something that is very hard to do as a Republican in this county - he has been elected to office before. That has to give him the edge."

Despite his background and his aggressive stances on many issues, Keeney is still remembered by some party workers as a plodding, sometimes indecisive council member whose moderate positions often led him to swing over and vote with the Democratic members of the council.

"There were three Democrats and three Republicans on the council," said one GOP central committee member, who has not yet decided on his vote in the primary. "Keeney was the swing vote. He would just as often Democratic as Republican."

"He will have to intensify his campaign if he's nominated," the committeeman said. "He's going to have to fall back on traditional Republican lines. He's a pipe-smoking, cool, collected guy, and many of us wish that he would get more excited."

Another regional precinct chairman, who said he intends to deliver all 12 of the precincts he manages for Ceccone, said many chairmen are leaning toward Ceccone in the primary because "He's aggressive and has done some nuts-and-bolts work."

"Keeney is like a Democrat turned Republican," the chairman said. "I never did see him at party functions during his inactive years, but all of a sudden he emerges. He never did anything for us, and now he wants us to help him. Well, we'll have to think about it."

Keeney himself is confident of a primary victory. He says "a substantial majority" of precinct chairmen are supporting him.

Keeney also has far more money to spend in the final days of the campaign than his opponents. By this week, he had raised almost $15,000, while Ceccone said he had collected slightly less than $9,000.

Already, largely ignoring Ceccone's attacks on his record and tax proposals, Keeney is focusing his campaign on the general election and the Democrats.

In a position paper described as "the first of a series of public announcements between now and the general election," Keeney depicted himself as an old-time fiscal conservative, once "a voice in the wilderness" who warns voters to "beware the new converts" of the Democratic Party.

Although he does not support the Committee for Tax Relief in Montgomery County (TRIM) to slash the property tax rate - a move Ceccone supports - Keeney has proposed a four-year package of 5 percent-a-year reductions in property taxes.