Tuesday was a good day for Democrats, as one candidate backed by the party won a special election to the Prince William County School Board and an initiative backed by the party passed overwhelmingly in Manassas.

Of course, Democrats’ biggest coup was helping push the swing, bellwether county toward President Obama. That helped him secure Virginia in his reelection bid.

With 99.5 percent of the precincts totaled Thursday, Obama was defeating Republican challenger Mitt Romney in Virginia by 1.89 million to 1.78 million votes, or a 3 percent margin. In Prince William, Obama led with 103,161 votes to Romney’s 74,371, the Virginia Board of Elections said.

Lillie G. Jessie, a retired school principal and owner of a business that works on educational issues, became the newest member of the School Board, beating four rivals for the Occoquan District seat. She had been backed by the Prince William County Democratic Committee, which had targeted the seat on the sometimes closely divided board.

“I think the public was saying to [the School Board], ‘We really want someone who . . . has some expertise in schools,’ ” Jessie said of her win.

She said the top priority she heard during her campaign was ensuring a rigorous curriculum.

“Not just as a school system, but as a nation . . . we’re falling behind in problem-solving, which impacts how our children are prepared to work in the global economy,” she said.

Jessie defeated Republican-backed incumbent Michael E. Wooten, who had been appointed to fill the seat left vacant when Grant Lattin retired this year. Jessie received 12,451 votes, or 47 percent, to Wooten’s 7,897 votes, or 30 percent. The seat is nonpartisan, per state law.

In Manassas, an initiative to move city elections from May to November passed overwhelmingly, receiving 8,922 votes, or 61 percent. The measure was backed by the Democratic Committee.

Republicans had urged voters to reject the initiative, saying elections would become more difficult and costly for candidates and could bury local issues under national ones.