As President Bush and Sen. John F. Kerry enter the final weeks of a tight presidential campaign, election officials in many key states are waging less noticed but equally partisan battles that could affect the outcome of the race.

In the battlegrounds of Ohio and Missouri, Republican secretaries of state have crafted election rules that Democrats say could disenfranchise legitimate voters likely to cast ballots for Kerry. Republicans say Democratic election officials in New Mexico and Iowa are making it easier for potential Kerry supporters to vote.

The disputed 2000 election cast a new light on the crucial role that secretaries of state play in crafting the rules that determine who can vote -- and whose votes are counted. Florida's then-secretary of state, Katherine Harris (R), was pilloried by Democrats when a series of decisions made by her office helped elect George W. Bush.

Election officials help determine what type of machines people use to vote, how ballots are printed, what identification voters must bring to the polls, how to get absentee ballots and countless other regulations. Already this year, with each party sensitive to every nuance of election law, issues as mundane as the weight of paper stock for new voter-registration forms are the source of controversy. Lawsuits have been filed or litigated in more than half a dozen swing states over state officials' interpretations of election law. Even in Maryland and Virginia, which are not battlegrounds this year, court battles have been waged over the role of state election officials and which candidates should be included on ballots.

"There's an unprecedented level of scrutiny," said Oregon's deputy secretary of state, Paddy McGuire (D). "Having an election decided by 537 votes in Florida made people see how decisions made by elections officials across this country can add up to electing the next leader of the free world."

Adding to the sensitivity is the fact that a number of chief election officials in key states are playing an active role in the presidential race.

Just as Harris served as co-chairwoman of Bush's 2000 Florida campaign, Ohio's J. Kenneth Blackwell (R) is co-chairing the president's effort in that state. Nevada's Dean Heller (R) and Arizona's Jan Brewer (R) are also active on behalf of Bush, as is Missouri's Matt Blunt (R), who is also running for governor. West Virginia's secretary of state, Joe Manchin III (D), is helping Kerry even as he runs for governor.

And while most election officials this year say they are determined to avoid the kind of partisan charges that dogged Harris for her role in the last presidential election, many of their decisions help the candidate whose party they share.

Take, for instance, a new federal law that requires all states to give voters whose names do not appear on the rolls a "provisional ballot" that will count if it can be determined after Election Day that the voter was properly registered.

Democrats see the provision as useful in correcting problems that caused eligible voters to be turned away from the polls in 2000.

Blackwell, Blunt and Republican election chiefs in Florida, Michigan and Colorado have been sued by Democratic groups for putting up hurdles in the counting of such ballots. Several, for instance, have ruled that ballots cast by eligible voters should be disqualified if they are cast in the wrong precinct, a move Democrats say disproportionately hurts poor voters, who may be more likely to move about.

Late last month, Blackwell came under fire for telling county election officials in Ohio to reject new voter registrations turned in on forms that do not meet an arcane law that mandates that the forms be on paper stock of a certain weight.

Though Blackwell subsequently said he would not enforce the law, Democrats and the League of Women Voters worry that his conflicting directives could cause confusion and prompt legal challenges in a state where the Democrats have signed up more new voters than the Republicans.

"I can't tell you what his motives are," said Ohio Democratic Party spokesman Dan Trevas, "but I can say that most of his actions help Republicans."

Blackwell counters that he also kicked third-party candidate Ralph Nader off the presidential ballot, a move that he said helps Kerry. As for the rest, Blackwell said he is just following the law.

"What you have here is a clash of ideals," he said. "There are those that believe a person should be able to register any time, on any form, and vote in any place. Then you have another point of view -- my point of view -- that says ours is a society of rule and law and rules have to be complied with to turn a ballot into a vote."

In Missouri, Blunt went to court this summer and quashed an effort by Francis G. Slay (D), the mayor of St. Louis, to open polls early in that heavily minority, Democratic stronghold.

Slay, a co-chair of Kerry's national finance campaign, argued that early voting was needed to prevent widespread disenfranchisement of city voters caused by long poll lines and other problems that occurred in 2000; Blunt argued that the mayor was trying to bend state law for partisan gain.

More recently, Blunt moved forward with a plan to accept ballots via e-mail from some overseas service members, a group that traditionally favors Republicans, despite concerns about the integrity of the system. And late last month, Blunt asked local election officials to send the state GOP weekly lists of those requesting absentee ballots, which were then used to contact voters, prompting Democrats to charge that he was ignoring a state law that prohibits contacting such voters for the purpose of advocating candidates.

Blunt spokesman Spence Jackson said, "You'd be hard pressed to find a more bipartisan secretary of state."

Sara Howard, Missouri spokeswoman for the Democratic group America Coming Together, said Blunt's gubernatorial candidacy raises a fundamental question: "Does he want to oversee elections in a fair, nonpartisan manner, or is he out to help himself and the president?"

Some election officials have tried to avoid such questions by refusing to campaign for their party's presidential nominee, but that has not inoculated them from criticism.

Florida Secretary of State Glenda E. Hood (R), for instance, eschewed the formal campaign role played by Harris but has come under criticism for a series of decisions affecting the election. Her latest move -- she issued a legal opinion that new registrations should be discarded if applicants signed an oath affirming their citizenship but forgot to check a citizenship box -- could bar thousands from voting.

Some local election officials, including those in Miami-Dade County, are ignoring the directive, and last Thursday, Democrats in Florida sued her in federal court, one of several cases pending on Hood's election-related rulings.

Hood's spokesman, Alia Faraj, said that Democratic interest groups signing up new voters are to blame for submitting incomplete applications.

In Iowa, Secretary of State Chet Culver (D) is under attack for sending out a voter guide that included an absentee-ballot request. Although the mailing went to every Iowa household, absentee voting in that state has traditionally favored Democrats, and Republican officials cried foul.

Culver said he is "offended" by Republican suggestions that distributing a voter guide to every Iowa household is aimed at anything other than increasing participation. "There's a big difference between a secretary of state putting out a voter guide and someone not accepting new voter registrations because of the weight of the paper," he said.

In New Mexico, state GOP Executive Director Greg Graves calls that state's chief election official, Democrat Rebecca Vigil-Giron, the "most partisan secretary of state I've ever seen." Vigil-Giron successfully fought off a GOP-led lawsuit that sought to require thousands of newly registered voters to show identification at the polls.

Graves said that twice as many new Democrats have registered in that state as Republicans, and he points to a $500 contribution that Vigil-Giron made to Kerry in concluding: "She feels the looser the rules are, the better it is for Democrats."

Vigil-Giron said she is just following the law. "In my heart and in my mind, I am a Democrat," she said. But when it comes to being secretary of state, she added, "I apply the law equally and fairly."

The D.C. region also has had its share of partisan sparring over election matters. In Virginia, Attorney General Jerry Kilgore (R), who plans to run for governor, pushed to place Nader on the ballot, a fight he won after the state's highest court ruled that Democratic election officials improperly disqualified Nader petitions.

In Maryland, the Republican-led State Board of Elections is trying to oust Administrator Linda H. Lamone, a Democrat. Her party has called the bid an openly partisan maneuver led by Gov. Robert L. Ehrlich (R) to give Republicans control over the state election apparatus.

In the swing state of Minnesota, Secretary of State Mary Kiffmeyer (R) is fed up with the partisan sparring. Liberal groups have charged her with attempting to stifle voter turnout by failing to keep up with the demand for new voter registration forms, rushing into service a flawed statewide registration system and issuing warnings about terrorism at the polls.

Kiffmeyer said her record speaks for itself: Under her watch, the state has had among the highest turnouts in the nation. "But I have the sense that if I walked on water, the Democrats would say I can't swim."

Researcher Lucy Shackelford contributed to this report.

Ohio Secretary of State J. Kenneth Blackwell (R) barred some registration forms over the paper.Secretary of State Chet Culver (D) sent a voter guide to every Iowa household and drew GOP fire.