For nearly 20 years, the well-educated and predominantly Democratic voters of Montgomery County's 8th Congressional District have made a habit of choosing liberal Republicans to represent them in Congress. The tradition began with Charles McC. Mathias in 1960 and continued with Gilbert Gude in 1968.

When Newton Steers was elected to the post two years ago, it was with the expectation that he would carry on in the Mathias-Gude fashion. Steers says he has. His leading Democratic opponent, Michael D. Barnes, says he has not. And therein lies the first and perhaps most basic issue of the 1978 8th district campaign.

"The idea that Steers is a liberal like Mathias and Gude is more myth then real," Barnes argued during an interview yesterday at his Silver Spring campaign office. "Here's a guy who supports the deregulation of natural gas prices and supported the Clinch River nuclear breeder. The Montgomery County congressman has traditionally been out front on environmental issues. Steers hasn't."

Barnes, who has been endorsed by virtually every Democratic leader and interest group in the county and is ignoring his four opponents in the Sept. 12 primary, raised the question of Steers' liberal credentials yesterday before a press conference he called to attack the incumbent congressman's support of the Kemp-Roth bill.

That measure, defeated on the House floor last week, called for reduction of federal income tax rates across-the-board by about 33 percent over three years. It has been promoted by the Republican leadership as the minority party's answer to the Proposition 13 mood in the country.

Barnes called the measure a "simplistic meat-ax approach to tax problems" and charged that Steers was "terribly irresponsible" for cosponsoring it and voting for it last week.

"Both President Nixon's and President Johnson's Chairman of the Council of Economic Advisors, Herb Stein and Walter Heller, have denounced the bill as inflationary," said Barnes. "And the Library of Congress Congressional Research Office, headed by Steers' predecessor, Gilbert Gude, has determined that the bill would result in higher inflation, higher interest rates and a larger federal deficits."

Steers, reached on the House floor yesterday, said he would not respond to Barnes' charges "in any way, shape or form until and unless he's nominated." He added: "I'm busy being a congressman. I'm not campaigning. Let them campaign." Steers is unopposed in the Republican primary.

The first-term congressman did take exception, however, to Barnes' attemtp to portray him as a conservative. "I am in the Mathias-Gude mold and I feel very comfortable with it," he said. "I have been invited by many Democrats to become a Democrat and I've been invited by even more Republican to become a Democrat."

As examples of his progressive politics, Steers noted that he voted against the neutron bomb supported neutron bomb supported Rep. Parren Mitchell's (D-Baltimore) effort to transfer $4.3 billion from defense to health and education budgets and was one of only two Republicans to vote in favor of the House's federal budget resolution this year.

Steers was by no means the only liberal Republicans to vote for the Kemp-Roth bill last week. In fact, only three Republicans voted against it - Millicent Fenwick of New Jersey, Paul Findley of Illinois and Charles W. Whalen of Ohio. A total of 37 Democrats voted for the Republican backed measure, which failed by a 177-to-240 vote.