Republican candidates appeared poised late Tuesday to make significant gains on the Loudoun County Board of Supervisors, in an off-year election that included several highly charged races on the county board and School Board, as well as in local law enforcement.

If a Republican majority is elected to the county board, voters can expect their new leaders to favor “smart growth” and economic development, with a renewed focus on attracting businesses to the fast-growing county, according to Loudoun County Republican Committee Chairman Mark Sell.

Hours after the polls closed Tuesday evening, election results were still coming in slowly. With 70 of the county’s 77 precincts reporting unofficial results, it appeared that Republicans could claim a majority of the county board’s nine seats. In all, election officials in the county estimated that about 30 percent of registered voters would decide the fate of more than 50 candidates competing in local races.

Unofficial numbers also showed Republican Sheriff candidate Mike Chapman maintaining a strong lead over four-term incumbent Sheriff Stephen O. Simpson, while independent Ron Speakman trailed well behind. And in the race for commonwealth’s attorney, incumbent James E. Plowman (R) and Democrat challenger Jennifer T. Wexton appeared neck and neck.

All the contests are profoundly affected by Loudoun’s rapid growth — the county is among the fastest growing in the nation — as local leaders face challenges related to development, traffic, crowded schools, a broader spectrum of crime and the rising costs of a growing community.

Among the most heated of Loudoun’s contests was the sheriff’s race, where questions of character became a central focus, as Simpson fielded criticism over campaign donations and his ties to a private beverage company, while Chapman and Speakman exchanged pointed accusations over each other’s professional experience and personal integrity.

The sheriff’s race also was among the most expensive in Loudoun. Speakman and Simpson each spent over $100,000, and Chapman spent around $42,000, according to campaign finance records.

Simpson greeted a slow but steady trickle of voters in the sunny parking lot outside Emerick Elementary in Purcellville Tuesday morning. But inside the school, several residents voiced support for Chapman, the Republican opponent.

One woman, who asked that her name be withheld because she works in local law enforcement, said “there need to be changes made” to the Sheriff’s Office.

“The morale in the office is horrendous,” she said. “Given our choices, Chapman is the best one.”

In the days leading up to the election, Democratic and Republican officials expressed hope that voters would refer to the county’s political history before casting ballots for the Board of Supervisors.

Republicans anticipated that voters would be displeased with the board’s recent economic development record, but Democrats hoped that residents would remember the period of rapid development and allegations of public corruption that prompted voters to sweep a majority of them into office in 2007.

With results from numerous precincts still outstanding late Tuesday night, many of the School Board races appeared particularly close. Volunteers from two schools-focused political action committees — Western Loudoun Schools and Educate Loudoun — were present at precincts across Loudoun Tuesday, wrapping up months-long efforts to draw more public attention to the often-overlooked School Board contests.

The winners of those races will face an array of challenges in the coming term, including the mounting pressure of a soaring student population and the demand for new schools.

Despite some reports in Northern Virginia of voter confusion resulting from the recent redistricting, Judy Brown, Loudoun’s general registrar, said the county was generally unaffected.

“I haven’t heard that there are people ending up at the wrong place,” she said, noting that only six precincts in Loudoun were directly affected by redistricting.

There were scattered reports of problems with touch-screen voting machines at precincts across Loudoun early Tuesday, Brown said, adding that paper ballots were available as an alternative.