After months of campaigning that apparently has left half the voters undecided, two of three Democratic candidates for Montgomery County executive have concluded that the race will likely be decided Tuesday by their volunteers' sales pitches to voters approaching polling booths.

Both the camps of State Sen. Charles Gilchrist and Montgomery County Planning Board Chairman Royce Hanson have scheduled volunteers, well-known in their neighborhoods, for each of the 170 polling places.

By contrast, County Council member John Menke, who has run a leaner campaign than his opponents, expects his workers at 50 to 70 precincts.

"Often it's on the strength of who's there passing out literature that voters make their decisions," said a Gilchrist worker.

On the same theory, Hanson has projected that about 5 percent of the voters will arrive at the polls undecided, a margin of about 4,000 votes that many observers of this contest believe could determine the outcome.

"We're just holding our breath, crossing our fingers and figuring that someone will win by 1,000 votes," a Menke supporter said.

This uncertainty has pervaded virtually all the county races in Tuesday's Democratic and Republican primaries, from the legislature to the nonpartisan school board. Many candidates blame it on the host of competing candidates who are running on numerous slates, sometimes conflicting, sometimes overlapping.

In addition, in several County Council and legislative races and in the state's attorney contest, vigorous challengers, powered by their supporters' desire for change, have forced incumbents to campaign as never before.

In the gentlemenly race for county executive the chief issue has been who is more qualified to run the office - Gilchrist, the tax lawyer and one-term state senator; Hanson, the former professor of government and planning board executive, or Menke, the physicist and one-term council member.

"On the face of it, it's not obvious that one or two of us is unqualified," said Menke. "None of us is off the wall or anything."

As they began publicly debating their issues, Hanson conceded to a reporter, "There's not that much difference between us."

Hanson's strategy has focused on presenting himself as a manager, running with a council slate to stress the importance of the two bodies working together and the "experience" theme that he believes he and at least three of his four incumbent teammates represent.

Gilchrist, on the other hand, has emphasized the "fresh image" he could bring to county government and the wide assortment of interest from whom he has received endorsements - from county government workers to unions, civic associations and tenants.

Menke has presented himself as a candidate who already has dealt with many of the issues the executive will encounter because of his four years working on the County Council.

In the latest independent poll conducted in the contest last week, the Montgomery Sentinel newspaper put Hanson and Gilchrist 15 percent of the vote and Menke at 14 per cent with 55 percent undecided.

A Gilchrist poll a week earlier had given Gilchrist 32 percent to Hanson's 24 percent and Menke's 14 percent, with 31 percent undecided.

But Gilchrist's pollster Richard Nugent was sufficiently concerned by the Sentinel poll and two Hanson tactics last week - an endorsement by County Council President Elizabeth Scull and a Hanson flier camparing the three candidates' experience - that he began repolling the "undecided" respondents over the weekend.

Interviews around the county confirm the candidates' assumptions that voters feel helplessly inundated with issues and pieces of political paper.

In Potomac, Ginny Hani said after a candidates' coffee, "A lot of my friends haven't made up their minds yet. They are really reading these brochures."

While in Rockville, a cafeteria worker told a candidate asking her to get her neighborhood vote out, "If I can . . . But they say, 'Oh, what's the use?'"

A similar sentiment pervades Republican precincts where workers have discovered widespread apathy. Time and again, voters said they did not know that Republican County Executive James Gleason, who has held the office for eight years, is not running again. "They said they were voting for Gleason," said on Republican volunteer.

The three Republicans seeking to replace Gleason are more sharply different than their Democratic counterparts.

Albert Ceccone, a realtor, and Gerald Warren, a lawyer, have both endorsed the Taxpayers' League ballot referendum to roll back property taxes, and have accused the third candidate, Richmond M. Keeney, of being a Democrat in disguise.

Like the Democratic executive candidates, Keeney, a planning commissioner, former council member and insurance executive, has opposed the Taxpayers' League proposal, preferring instead a gradual reduction in taxes.

Although the Taxpayers' League proposition will not appear until the November general election ballot, the possibility of a taxpayer's revolt over rising assessments has crept into every campaign.

In fact, the fieriest election issue emerged unsuspected two weeks ago when the County Council proposed, and under political pressure, quickly withdraw, a plan to raise income taxes to relieve a part of the burden of the property tax.

That political gaffe just 10 days before an election gave Council member Jane Anne Moore, the one incumbent to be dropped by the Montgomery Democrats slate of party regulars, the issue she needed, according to some Democratic officials.

Moore, who has been unpopular among her council colleagues, was absent from the council discussions preceding the request for the tax increase and she has denounced the proposal at every opportunity.

Mike Gudis, a partner in a financial management firm and a member of Hanson's slate, and W. William Whitacre, a Silver Spring business man, are trying to defeat her.

In spite of the contest over Moore's seat, most of the 15 Democratic and 12 Republican campaigns for seven county council nominations in each party have been contests in name recognition.

Although the themes of schools, landwill sites and taxes are frequently cited by voters as the most pressing concerns, "usually we talk about our backgrounds," said Sally Kanchuger, an at-large candidate. "Each of us believes we have a lot to offer, and there still is a lot of bewilderment about who the candidates are and what they stand for."

Her at-large opponents are Rose Crenca, Scott Fosler, Mable Granke, Tom Hamilton and Nathan Wilanksy.

The one possible exception to this pattern has been the race between incumbent Esther Gelman and Alvin T. Scheneyr, a tenant activist allied with Jane Ann Moore. "She alone (Gelman) is taking a lot of grief" for the council's decision to end rent control last year, observed one party watcher. "There's been a lot of acrimony in that race."