It’s official: Elizabeth Davis is the new president of the Washington Teachers Union and will lead contract negotiations on behalf of 4,000 D.C. teachers.

Davis took office Thursday after unseating incumbent Nathan Saunders in a runoff election last month. Saunders appealed that result in an effort to hold onto his seat, but has now withdrawn his challenge, he wrote in a farewell letter to union members Wednesday.

“You have made a choice which I shall respect despite some technical nuances,” Saunders wrote, adding that given the challenges the union faces — including an existential threat from the closure of traditional schools and the rapid growth of charters — “leadership is primary and who provides it is secondary.”

Saunders chided his colleagues for apathetic involvement in union issues, a problem he said is symbolized by low turnout in the union election. Of 4,000 teachers, only 65 percent, or about 2,600, are full dues-paying members and therefore eligible to vote, he wrote. Fewer than 900 teachers actually submitted ballots.

“A lethargic membership is more cancerous than reforms, charter schools, and excessing,” Saunders wrote. “Members’ expectation of any president must be tempered with what they are willing to do for themselves.”

Saunders had been close to reaching a contract deal with school system officials that reportedly included salary increases and provisions, favored by Chancellor Kaya Henderson, that would allow for a longer school day and year.

Henderson said this week that extended school time remains one of her top priorities for the new contract, and said seven of eight schools that experimented with longer school days this year increased their test scores in math and reading.

Davis, meanwhile, has said she’s not convinced that longer school days are the best way to lift student achievement.