With economic issues such as taxes, jobs, inflation, business development and government spending among, the top concerns of average citizens, it is no surprise that business persons are getting involved in politics.

Legal donations by business organizations to candidates now rival similar contributions by organized labor. And, in the D.C. area, the largest business group - the Metropolitan Washington Board of Trade - has begun supporting specific candidates and making donations in the city, Northern Virginia and the Maryland suburbs.

A good example of the new business interest in politics is Maryland State Senate District 15 - the largest in Montgomery County and the fastest-growing since 1970. It stretches across the northwestern part of the county from the fancy estates in Potomac to the suburbs of Rockville and including the broad stretch of rural land up to the borders with Frederick and Howard counties.

Seeking votes from some 70,000 registered voters in the 15th District are:

The incumbent, Democrat Laurence Levitan, a lawyer who was elected to the Senate in 1974 after several years in the House of Delegates.

Republican John Henry Hiser Jr., a homebuilder and president of the Potomac Chamber of Commerce.

Independent Bette Marshall, founder and co-owner of Yesteryear Farm, an antiques and furniture business near Laytonsville and mother of 15 children.

All three of the candidates said this week they expect to be elected next Tuesday but maverik Marshall's entry into the race is thought to be a significant factor in what may be a close race.

Both Levitan and Hiser said they don't think the independent store owner has a chance of winning, but both said she's making it more difficult for the Republican candidate.

One Hiser supporter asked Marshall to withdraw and throw her support to the GOP candidate. And the rival Hiser and Marshall camps have been engaged all week in a game of signsmanship in downtown Gaithersbury.

The fight over signs deals with Marshall campaign headquarters on the second floor at 309 N. Frederick Ave., and Hiser signs in front that they have put up, torn down and put up again by various parties. Marshall called it "dirty pool" and Hiser said he didn't put the signs there.

Hiser also said he thinks that Marshall "certainly" is stealing votes from him but that the attempt by his supporters to have her withdraw was not done at his direction.

A Hiser pool conducted two weeks ago indicated a close race between the builder and incumbent Levitan, with a margin of 1 to 3 percent in Hiser's favor and Marshall attracting less than 10 percent.

Levitan said he expects to win by a clear majority over his two opponents, "rather than a plurality . . . but I think it's frustrating for the Republican candidate." The Democrat said he expects to win by attracting independents as well as his party's majority in the district - partly because the legislature itself will be controlled by Democrats and "it's important for the county" to have his representation in Annapolis, where he may become chairman of the budget and tax committee.

Marshall does not regard herself as a spoiler, although many of her views parallel those of Hiser; for example, both support TRIM, a local tax-limiting measure opposed by Levitan. Financed initially by a $1,000 donation from her husband and a $5,000 bank loan, former Democrat Marshall decided to enter politics because of her belief that government lacks the disciplines she has used in her small business.

"I think we have a heck of a good chance," said Marshall, who has been aided in her campaiging not only by the large family but also an army of volunteers. "With the revolt in this county," she added, independents, Republicans and Democrats all are seeking candidates with "common sense" approaches to government and taxes.

Hiasser also talked of revolt. There' a feeling across the state that people are prepared for a change . . . the people are fed up with the way government has been run the last eight years," said the GOP candidate, who has been speaking at up to two coffees a day since the primary.

In terms of endorsements, Levitan clearly is the winner at date. The Board of Trade's political committee for Maryland contributed to him on Thursday, noting that it favored persons who favor economic growth. The county education association, fearful of TRIM, endorsed him as did - despite Hiser - homebuilders.

Among several newspaper endorsements, Levitan said he was favored by the Montgomery County Sentinel - but the lines of type with that endorsement were inadvertently deleted from the paper this week. By next week, it will be too late.