DES MOINES, Oct. 27 — More than 6,000 state legislative seats in 46 states are on the Nov. 7 ballot, and like the seismic state elections in 1994 and 1974 the cumulative impact of the outcomes could be immense, with Democrats possibly gaining control of a majority of state capitols for the first time in a decade.

While the nation's attention has been fixed on the question of which party will control Congress, another campaign season has been unfolding in the shadows — upstaged and overlooked but more likely to affect the day-to-day life of voters than the big-money Congressional races.

Most significantly, the groundwork for redrawing Congressional districts after the 2010 census will be done under the 50 capitol domes, and the party in power will set the table for those discussions in ways favorable to its interests. Gains made this year, analysts say, will help give incumbents a leg up in the final elections leading up to the redistricting.

If the Democrats take control of a majority of the legislatures, which polls indicate could happen, women could also attain leadership positions in greater numbers, since Democratic women in state capitals outnumber Republican women by nearly two to one. The next generation of national political leaders, by tradition, is nurtured in the state legislatures.

"This is a national election with big issues," said Alan Rosenthal, a professor of political science at Rutgers University who tracks state election issues, "and that will filter down to the people who nobody knows about."

One indication of both parties' interest in the local races is the money that has been flowing into them.

The Democratic Legislative Campaign Committee plans to spend $9 million to $10 million on legislative races, up from $6 million to $7 million in 2004. Its counterpart, the Republican State Leadership Committee, has nearly doubled spending on state races, including for legislators, to $20 million.

Republicans control both chambers in 20 states, Democrats in 19. One state, Nebraska, has a nonpartisan legislature, while the parties split control in the remaining 10 states. States to watch on Election Day include Indiana, Iowa, Michigan, Minnesota, Nevada, Oregon, Pennsylvania, Tennessee and Wisconsin, where Republicans have narrow majorities in the lower house or senate. Democrats have narrow majorities in Colorado, Maine and Montana.

What makes the races even more suspenseful is that the parties have not been so even in decades, if ever. Of the 7,382 statehouse legislative seats across the country, Democrats hold 21 more than the Republicans, a margin of less than half a percent.

In 17 of the 46 states that will elect some or all of their state senators, a shift of only three seats would alter party control in the senate, according to the National Conference of State Legislatures. In 12 state houses, a shift of five or fewer seats would tip the balance.

Some states, like Montana and Colorado, where Democrats gained narrow legislative control for the first time in decades in 2004, are being watched by some political scientists and party leaders as barometers of the party's Western strategy. Other states with closely divided legislatures, including Michigan, Nevada and Tennessee, could be swung by fierce contests for governor or the United States Senate.

Connecticut and New Jersey, where Democrats control both chambers of the legislature, and New York, where the parties each control a chamber, are not widely expected to see shifts in power. "We seem to be in this era of hyper-evenness of the parties at the grass-roots legislative level," said Tim Storey, a senior fellow at the National Conference of State Legislatures.

Presidential hopefuls have also poured several hundred thousand dollars into legislative races in Nevada in anticipation of the early presidential caucus there in 2008. In Michigan, a new group sprang up this year, the Michigan Coalition for Progress, to help defeat Republicans in the legislature.

And then there is Iowa, where the hyper-evenness is most hyper of all. Republicans have a one-vote advantage in the Iowa House, 51 to 49, and the parties are tied at 25 in the Senate.

Noticing these whisker-width margins, prospective presidential candidates, including Gov. George E. Pataki of New York and Gov. Mitt Romney of Massachusetts, have donated money to local campaigns, hoping perhaps to make friends before the Iowa Caucuses in 2008.

Mr. Pataki's political action committee has donated $270,000 to Iowa Republicans, Mr. Romney's PAC almost $1.6 million, according to the Iowa Ethics and Campaign Disclosure Board. Independent political groups, called 527s, have waded in as well to influence or swing the vote.

But the money and the high stakes, many people here say, may be having another effect in Des Moines and many other state capitals. State legislative races, with their low-glamour blend of amateur politics and homespun local concerns, may be losing their traditions of civility.

"You have more money sloshing around," said Peverill Squire, a professor of political science at the University of Iowa who follows legislative races. More and more, Professor Squire said, control over local campaigns is slipping toward centralized parties or interest groups. "And it is certainly a much rougher campaign than we are used to seeing in Iowa," he said.

Just ask Kevin R. Wiskus.

Mr. Wiskus is a 42-year-old Iowa farmer and lifelong Republican from the town of Centerville, about 100 miles south of the capital, who is making his first run for public office for a House seat.

He became so outraged by his own party's efforts to elect him that he resigned last month in protest.

A mailing sent by the state committee told voters that Mr. Wiskus's Democratic opponent, a lawyer named Kurt Swaim, had defended a man charged with child molesting.

Mr. Wiskus knew that Mr. Swaim had been assigned the case by the court as a public defender, and decided the attack was unconscionable. He is now an independent, and said he would serve as an independent if elected.

"I was offended," Mr. Wiskus said in an interview. "I had promised and pledged to run a clean and ethical and honorable race, and I told the Republican Party I did not want any attack ads."

The speaker of the Iowa House of Representatives, Christopher Rants, a Republican who has marshaled the party's efforts in the legislative races, said he thought the Democrats had done more than his party to coarsen the debate in Iowa with negative advertising.

One mailing about a Republican, Mr. Rants said, showed a cadaver under a sheet and suggested that the candidate's opposition to stem-cell research was responsible for the woman's death. Democrats and some independent scholars, including Professor Squire, say the Republicans have probably pushed the line harder and farther.

Whether the Republicans can hold onto the gains in state legislatures that they made beginning in the 1980s is probably the central question of the election.

The Democrats, for most of the 20th century, were statehouse titans all over the nation — with a peak in the mid-1970s when they controlled close to 70 percent of all legislative seats. In the post-Watergate election of November 1974, they added 628 legislature seats in just one night.

The Republicans began a surge in the 1980s, making major strides in 1994, when they gained 514 seats overnight. They finally gained dominance in 2002, picking up enough seats to surpass the Democrats for the first time in 50 years. There has been almost perfect parity since then.

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