By many political measurements, Bill Curry, 30, a Democratic state senator, should be the next congressman from the open 6th Congressional District in northwest Connecticut.

Democrats, most recently the popular Toby Moffett, have held the seat since 1971. Almost every week, another aging factory in the district shuts down or lays off workers, dramatizing Curry's ceaseless talk about jobs, the recession and his opponent's ties to President Reagan.

Curry has been targeted for help by environmental organizations and by most women's groups, even though his opponent is a pro-Equal Rights Amendment woman.

Despite all this, with Moffett running for the Senate this year Republicans stand a good chance of winning what has become one of the most hotly contested races in the country. They have a strong candidate with a record of attracting Democratic votes, State Sen. Nancy Johnson. And, with White House help, they have an almost overpowering 2-to-1 lead in fund-raising.

"It's a tough one," Sen. Christopher J. Dodd (D-Conn.) said as he campaigned for Curry last week, shortly after a GOP poll showed Johnson leading by 10 points with 24 percent undecided. "Reagan should be more of an issue, but when you can spend $400,000, you can do a lot of convincing that he's not an issue." Both candidates are seen as rising stars in their parties, although they have taken different routes.

Curry's first word as a baby was "vote," according to family lore, and he was elected to the state senate when he was 26. Johnson, 47, raised three girls before entering politics, and points to her United Way service to show she understands government-private sector partnership.

The district includes struggling old manufacturing cities like Bristol, New Britain and Torrington, centers of ethnic Democratic politics and United Auto Worker union work.

Pockets of unemployment in the district have soared above the national average of 10.1 percent as ball bearing and machine tool plants move south or overseas. About 40 percent of the registered voters are Democrats, with the remainder split evenly between Republicans and independents. It is a difficult district in which to campaign because it includes so many media markets.

But Johnson has been advertising on Hartford and New Haven television stations. The image she is selling is that of a compassionate moderate, an independent-minded woman who can balance her zeal for cost-cutting with a deep concern for people -- a candidate, in other words, without the Reagan taint. The word "Republican" does not appear in her ads, and her first statement at debates is, "I am not here as a spokesman for the president."

She frequently refers to the 3-to-1 Democratic majority in the New Britain district that has elected her three times. When Vice President Bush came to help her recently, he raised $40,000 at a lunch in Hartford--and never came to the district.

Curry points incessantly to Johnson's position as co-chairman of Reagan's 1980 Connecticut primary campaign and to some of the pro-Reagan statements she made during her tough primary battle. He attacks her support for Reagan's budget as though she were an incumbent who had voted for it on Capitol Hill.

But Curry has to make those attacks before small groups at senior citizen centers and women's clubs, because he has had no television advertising and may have none before Tuesday's election. With no polling and no computerized mailing, his campaign is technologically in the political Stone Age, relying on union telephone banks and Friends of the Earth volunteers who "crash" in other volunteers' houses.

"What we have to combat them with is leafletting," Curry says, "and I'm not sure in an age of television how many people read leaflets."

Johnson discounts what her press spokesman calls Curry's "whining" about money, pointing to his solid union support and her defeat of a primary rival who spent more than she did. "If he's having trouble raising money, maybe that says something about his message," she says.

Johnson's finance director says her campaign has raised about $260,000, having spent $160,000 prior to the Sept. 7 primary. Curry has raised $120,000, his campaign manager said, and spent $90,000 on the primary. The money has helped Johnson project the personal traits she must depend on to win in the Democratic district.

"She's a woman, she's got a lot of guts, she's got a lot of spunk," said steelworker Bill Schreier after Johnson had shaken his hand outside a Southington supermarket. Schreier said he is a Democrat, a supporter of Toby Moffett, but had seen Johnson on TV and would vote for her. And Curry? "I don't know," Schreier said. "I don't know him personally."