David LaRock was able to oust 20-year incumbent Virginia Del. Joe T. May in the June GOP primary by touting conservative credentials and assailing May’s vote for a transportation funding bill as evidence of wasteful spending. In a decisive upset, the Hamilton businessman was elected the Republican nominee by Virginians who agreed with his claim that May was soft on issues such as taxes, abortion and gun rights.

But LaRock’s opponent in the general election is trying to use the candidate’s ideology against him, saying he doesn’t represent the majority of voters in the House’s 33rd District.

And with public opinion increasingly turning against staunchly conservative members of the GOP as a result of the federal government shutdown, Democrat Mary Costello Daniel said she sees an opportunity for the historically Republican territory to swing blue.

The sprawling district includes much of western Loudoun County, a bellwether jurisdiction that has been watched closely in recent local and national elections. In 2008 and 2012, Loudoun and the commonwealth were carried by President Obama — the first Democrat in decades to win the state in a presidential election.

Daniel, an attorney and member of the Berryville Town Council, said May’s defeat prompted her to enter the race.

“Joe May was capable of reaching across the aisle and treating people respectfully in order to find common ground, and I think that was manifested in the transportation bill,” she said in an interview. Voters “want to have the assurance that my intention in Richmond is to serve them, and not to dig my heels in and pronounce ultimatums and join a minority that would create a roadblock, as the tea party is doing in Congress right now.”

Mark Rozell, acting dean and professor of public policy at George Mason University, said the partial government shutdown could influence the race in an area home to many federal workers.

“These outer suburb districts are so critical in Virginia elections now,” Rozell said in an interview. “To the extent that the Democrats can continue characterizing the current climate . . . as driven by an extremist element in the Republican Party, I think that hurts the GOP’s chances both within this district and statewide.”

But LaRock said he has momentum after defeating May, which he said was a sign that people in the district want more fiscally conservative leadership and a stronger economy.

“I think my background in business gives me firsthand understanding of what makes businesses tick in the areas of taxation, regulation and policy,” he said. “So for focusing on economic issues, that makes for a very good fit. . . . I know how to be a problem-solver and job creator.”

LaRock said in an interview that he would champion a move toward “performance-based spending” in all areas of government, including transportation, education and public safety — focusing funds on projects with a clear and measurable benefit, he said.

“Pretty much everyone is interested in seeing the economy recover, and they want to see taxes and spending kept in check,” he said.

Daniel said she would focus first on transportation projects if elected, and would also like to review some of the funding cuts made during previous General Assembly sessions.

“We had a surplus this year, so there’s no need to be raising taxes,” she said, “but we just need to make sure that the budgeting process is done properly, so that we can restore funding where it has been so severely cut in the past.”

As the Nov. 5 election approaches, both campaigns have focused on topics such as economic recovery and job creation — and LaRock has steered away from some of the social issues addressed during the contentious primary.

“I state my position on social issues so that people will understand me and my character, but as a legislator I would be focusing on economic issues,” he said.

But Daniel said LaRock’s socially conservative views still matter to voters. A recent mailer distributed by the Democratic Party of Virginia declared in bold print: “Dave LaRock supports a plan that could force police to investigate women who suffer a miscarriage,” referring to a failed 2009 state Senate bill introduced by Republican Attorney General candidate Mark D. Obenshain that would have required women to report a miscarriage within 24 hours or risk criminal penalty.

LaRock called the mailer a “baseless smear piece,” saying he hadn’t heard of the bill.

“I think having a campaign based on background, track record and real issues is what people want,” he said. “I’m very disappointed to see [Daniel] moving in that direction.”

In recent weeks, Daniel and LaRock have ramped up their public appearances and secured competing endorsements from influential local officials and organizations. Both campaigns have also heightened fundraising efforts — with LaRock’s campaign securely in the lead, reporting more than $100,000 in contributions since the primary election, campaign officials said. Daniel has pulled in just over $52,000, according to campaign finance records. A third candidate, Libertarian Patrick Hagerty, has maintained a zero balance in his campaign coffers, records show.