Nathan Saunders, the Washington Teachers’ Union president who lost his reelection bid early this month, is seeking to invalidate that result and force a new round of voting.

Saunders was defeated July 1 in an upset by Elizabeth Davis, a longtime union activist who promised to be more forceful about challenging D.C. Schools Chancellor Kaya Henderson.

Saunders has filed an appeal, arguing that the contest was skewed because of rules violations, including, he alleges, Davis’s unfair campaign tactics and improper voting by teachers who retired or were fired before ballots were counted. Saunders said his 459 to 380 runoff defeat should be thrown out.

Davis is slated to take office Aug. 1, but Saunders argues that he should remain president until the union’s elections committee resolves his complaints.

“I’m optimistic, actually,” Saunders said of his chances of prevailing.

Davis dismissed Saunders’s claims as an illegitimate power grab and said she would take office as planned.

At stake is the right to negotiate a new contract on behalf of 4,000 District teachers.

Saunders has said he is close to reaching an agreement that would include salary in­creases and provisions for longer school days. Henderson has said longer school days are critical for improving student achievement.

Davis said she cannot comment on how she plans to proceed until she sees the pending contract language. But she said she is skeptical that more hours in school will translate into better outcomes for students.

“I think it’s worth examining that and seeing how we make it a better school day, not a longer school day,” Davis said.

She and Saunders were among four initial candidates for WTU president. None won a majority of votes in the first round of balloting, forcing a runoff, which Davis won by 79 votes.

Saunders said that tally was flawed because the elections committee sent ballots to 350 teachers who retired on or before June 30, making them ineligible to vote.

In addition, 54 teachers wrongly received ballots after they were fired in June for poor performance, Saunders wrote in his appeal, as did 89 teachers who lost their jobs as a result of budget cuts.

It was unclear how many of those teachers actually submitted their ballots for counting. School system officials declined to comment on those figures.

Saunders also alleged that Davis violated union rules when she asked principals to announce to teachers the date and time of a campaign event.

Davis acknowledged that she had asked for that help. But “not one teacher showed up” to that event, she said. “Anybody would see that did not have an impact on the outcome of the election.”

Finally, Saunders argued that he is entitled to remain president until December 2013 because the union constitution says terms should begin on July 1 and are three years in duration.

Saunders took office several months late, in December 2010, because of a delay amid union infighting: Then-President George Parker had refused to hold elections, forcing the national parent organization, the American Federation of Teachers, to step in.

Saunders acknowledged that he could have challenged the timing of this year’s election earlier, before votes were cast. But he had expected to win.

“A lot of folks were quite surprised with the results, including myself,” Saunders said.

There is no deadline for a decision from the union’s elections committee. Candidates may appeal that local ruling to the AFT.