Montgomery County political candidates begin their traditional, frenetic last-minute primary campaigns this week, facing a 30 percent turnover in the electorate since 1974 and polls indicating that half the voters still are undecided.

"On Labor Day, voters wake up to the fact that an election is coming up (on Sept. 12)," said one Democratic worker. "They unpack from their vacations, put their kids in school and sit down to read the campaign literature that has piled up on their doorstep."

That will be a lot of reading. About 150 candidates - from gubernatorial aspirants to the county school board - are running in the primaries.

Although Montgomery County is the home of Acting Gov. Blair Lee III, one of four Democratic gubernatorial candidates, those contesting for the Democratic Montgomery County executive nomination, the top local office at stake Sept. 12, have refrained from endorsing Lee or any of his opponents - Theodore Venetoulis, Harry Hughes or Walter Orlinsky.

In the county, where the Democratic Party has long been undisciplined, such allegiances could only heighten the primary election feuds that have denied them wins in the county executive and congressional races for years, according to party workers.

The choices this year also are compounded by a multitide of sample ballots distributed by numerous party factions - often overlapping, sometimes conflicting - in their endorsements.

"I'll tell you the truth," said one Democratic activist. "I've got so many slates in the mail at this point, I can't keep them apart, and I keep up better than most."

Most attention has centered on contests for county executive, a post Republican County Executive James P. Gleason is vacating after two terms.

Republicans Richmond M. Keeney, a member of the planning board; Albert Ceccone Jr., a realtor, and Gerald Warren, a lawyer, are seeking the nomination to replace him.

So are three Democrats, whose supporters believe their hard-fought "horse race" is an encouraging sign that for the first time in eight years, a Democrat could be elected to the office.

The Democratic county executive contest between state Sen. Charles Gilchrist, Planning Board Chairman Royce Hanson and County Council member John Menke, three progressive Democrats, has centered more on images than issues.

All three, for example, have opposed a ballot referendum to roll back property taxes and have called for limitations on government spending. When the first real campaign flare-up occurred last week in the form of a Montgomery County Council request to the state legislature for an increase in income taxes, all three Democrats promptly denounced the idea.

Gilchrist's supporters have stressed "fresh face" and untainted image as a state senator free of the strong friendships and animosities that Menke and Hanson have built up during their years in local office.

Yet, when Gilchrist indicated last month that he might fire Police Chief Robert J. diGrazia for the "low morale" of the police force and the decline in emphasis on traditional law enforcement functions, his opponents quickly pictured Gilchrist as an outsider unfamiliar with intimate details of the county's government.

Hanson's supporters, on the other hand, are emphasizing their candidate's long experience in management and government as chairman of the planning board for five years and as a professor of urban affairs and public administration for 17 years.

Hanson campaigners began blanketing the county Friday with 75,000 handbills comparing Hanson's experience with that of his opponents. On some columns where Hanson's former governmental and political positions amount to several lines of copy, there are large empty white spaces under Gilchrist's and Menke's names.

Menke, a one-term County Council member and physicist who has gone much farther in the race than most expected, is buoyed by his own momentum. "Starting from zero three months ago, the trend looks good," he said.

Disdaining organizational politics, Menke has built his campaign around a handful of volunteers. He appeared one day at the county dump to stress the need for better environmental controls in the county, then stood before the pit for the new $50 million county office building to demand that undue government spending be curtailed.

Unlike his opponents, he is against collective bargaining for county government employes.

The only executive candidate conducting polls is Gilchrist, the best-financed contender. His campaign's random sampling of 200-to-300 typical primary voters show Gilchrist's narrow lead slipping, as his two opponents gain strength.

The first poll two weeks ago showed Gilchrist with 22 percent, Hanson at 18 and Menke at 13; the second one week later put Gilchrist at 21 percent, Hanson at 19 and Menke at 14.

In 1970 and 1974, Gleason won despite a 2-to-1 Democratic lead in voter registration. His victories have been attributed partially to the infighting that historically has split the undisciplined Democratic Party after each primary. Some disgruntled Democrats went to work for Republicans.

Party chairman James Doherty has spent most of the year trying "to prevent the fratricide" after the primary.

A crucial maneuver occurred earlier this summer at two endorsement conventions of party activists. Before the meetings, the leadership agreed that a sufficient majority - 65 per cent of those voting - would be required to endorse an executive candidate, practically making endorsement impossible.

According to knowledgeable participants, when it appeared that Gilchrist would receive at least 65 per cent of the votes at the convention of the Democratic coalition, the word was passed around swiftly to supporters of Menke and then-executive candidate Scott Fosler to switch their botes to Hanson.

Consequently Gilchrist won 64 per cent - and no endorsement - to Hanson's 35 per cent. At the next convention of the Montgomery Democrats, Gilchrist received 60 per cent to Hanson's 40 per cent.

It was subsequently agreed that all executive candidates could appear on the Montgomery Democrats sample ballot, the slate of party regulars.

In the Republican executive contest, debate has centered on property tax relief. Keeney has denounced the November ballot referendum to roll back property taxes from 15 to 20 per cent. Instead, he proposed a more moderate reduction in the tax levy 85 per cent annually.

Ceccone, however, labeled Keeney as a "Democrat in disguise," and threw his support behind the tax referendum. "The people who put that on the ballot weren't reactionaries," said Ceccone.

Warren, who spend three years in the county attorney's office until 1976, has been working to alter his image as a political unknown.

Republican activists said they have found "very little thought" being given to the primary, in which about 30 per cent of the Republicans are expected to vote.

Keeney, the best-known candidate, has not campaigned with the "fire" some thought he should. On the other hand, Ceccone, his chief rival, has been what some activists call "too negative" by constantly attacking Keeney.

The Republican campaigns also are hampered by an "every-candidate-for-himself" attitude within the party because the Republican organization traditionally does not get involved in primary races. That means, according to one party worker, that "election-day activity counts for a lot."

Two other Democratic primary contests have attracted considerable attention.

Retiring County Council member Dickran Hovsepain has mailed several thousand copies of a letter vigorously opposing the reelection of Council member Jane Ann Moore. Hovsepain said Moore has not been "effective."

He endorsed newcomer Mike Gudis over the third primary candidate, W. William Whitacre. Moore called Hovsepain's charges "inaccurate."

An even more bitter contest is being waged in the Kensington-Chevy Chase area between State Sen. Margaret Schweinhaut and Del. Charles Docter for the District 18 Senate nomination.

Docter, an indefatigable campaigner and maverick legislator who has gained popularity for his consumer and environmental legislation, has blanketed the district with red yard signs reading, "This House Sold on Docter for Senator."

Schweinhaut, who is 73 and has represented the area for 23 years in Annapolis, reportedly was upset at the vigor of his campaign.