John Smith is Bill Brock's secret weapon.

A cheery, energetic 37-year-old political neophyte who is unknown even to most people in her legislative district here, Smith is one of the front-line troops in a $3 million crusade launched by Republican National Chairman Brock to cut into Democratic dominance of state legislatures from coast to coast.

She has been painting yard signs and pounding on doors for months in an effort to unseat the Democratic incumbent in Oregon's 9th Legislative District. It can be a trying task. In a year of national and statewide elections, a legislative candidate's lot is one of indifference and inattention. But one place Smith has not been ignored is at the Republican National Committee, across the continent in Washington, D.C.

Brock's committee and other national Republican groups have given Smith about a fifth of the $25,000 she has spent on her campaign. The national party has trained her campaign manager, sent three field workers into her district and mounted a tough direct-mail attack on her opponents.

Why?

Brock and Joe Gaylord, who heads the GOP's local election unit, say the aid given Smith and hundreds of other legislative hopefuls is partly designed to build a cadre of future Republican leaders around the country.

There is a more concrete and immediate reason, too, for Brock's legislative endeavor. Sometime next year, unless the federal courts delay things, the 50 legislatures will receive official tabulations of the 1980 census. And that will set the stage for one of the most intricate forms of political artistry -- the drawing of new districts for legislatures and the U.S. House of Representatives.

Michelangelo, with an uncut block of marble, had nothing on the artistry a partisan group of legislators can work on an unlined map. Brock asserts that the last redistricting, in 1971, when Democrats controlled 23 legislatures to 16 for the Republicans, cost the GOP about 40 seats in Congress.

The techniques employed in gerrymandering can be illustrated in a typical big city -- normally Democratic terriroty -- that is surrounded by a ring of suburbs -- normally Republican.

A Democratic legislature might divide the region into units shaped like wedges of pie, with the urban core containing more people than the suburban crust in every district.

The Republican solution might be a series of barbell-shaped districts, each containing two blobs of suburbs connected by thin strips through the city.

Brock is worried because the artists next year are likely to be mostly Democrats. Right now the Democrats control both houses in 30 states. The Republicans have 12 states, plus Nebraska, which is nonpartisan and unicameral but really Republican. In seven states the parties control one house each.

Nearly 6,000 of the country's 7,482 legislative seats will be at stake Tuesday, according to the National Conference of State Legislatures, but the Democrats seem sure to retain control in a majority of the states. The GOP's best hope is to set up a defense of sorts by winning one house in some states where they now control neither.

That's where Oregon's John Smith comes in. Democrats seem sure to regain the state Senate here, but the GOP needs only five new seats to take over the House. And Smith is one of the best hopes the party has.

Smith, articulate and civic-minded, has been active in local affairs ranging from the Junior League to the city planning commission. She was recruited for the legislature race last year by the state party. At first she resisted, but thoughts of the census changed her mind.

"The party always promises to help you like crazy," she said, "and then you never hear from them again. But I thought this year, with redistricting ahead, they would really take an interest."

When she launched her campaign last fall, Smith commissioned a name recognition poll in her upper-middle-class district.The pollster listed the names of Tom Mason, the incumbent Democratic legislator, Joan Smith, and one "Rolph Zabrisky," a fictitious character included to determine whether respondents were lying."

About 70 percent of those surveyed knew Mason's name; Smith scored 2 percent -- a point behind "Zabrisky."

But then Smith put together a campaign operation, headquartered in her dining room, and the state and national Republican parties came to her help with money and technical advice.

Elizabeth Dugan, a field worker form the Republican National Committee's D.C. office, was sent here last summer to look things over for a couple of weeks. She has never left. Dugan has taken over direction of the Smith district mail campaign, and turned it into a cannonade of criticism of the incumbent, Mason.

"The problem is," Dugan said, "when I got here, the district had two real nice people running against each other. And if nothing happens then the real nice incumbent is gonna beat the real nice challenger. So we had to adopt what I called an 'attack' strategy."

While Dugan was planning the attack, Smith spent her time walking to the 15,000 homes in her district. "This election will be won door-to-door," she said. "I go around just to meet people and ask them what they want from their state representative."

What do the voters want? "Most of them have no idea," Smith said with a sigh. "Be reasonable. Don't make a fool of yourself. Don't spend too much of their money."

Mason, a friendly, hard-working 36-year-old lawyer, has pursued the same tactic. The two candidates have made two joint appearances, with a total audience of fewer than 50.

For weeks, the two seemed to be competing toward a stalemate. Nothing Smith could do seemed to cut into the incumbent's base.

Then, last week, the Portland Oregonian endorsed Smith for the seat in a lavish editorial that said Mason was a decent person but Smith was the kind of candidate who only comes along once in a decade. "What a coup!" Dugan says now. "That editorial is going to make me a genious. We've got a great chance."