RALEIGH, N.C. — A conservative limited-government group is actively campaigning against Democratic nominee Deborah Ross in North Carolina’s U.S. Senate race.

Americans for Prosperity North Carolina announced Tuesday that it would send out more than 500,000 mailers and emphasize its opposition to Ross in its field activities. Ross is trying to unseat Republican Sen. Richard Burr in November.

The group often focuses on issues and does not directly work for or against a candidate. State AFP Director Donald Bryson says it’s targeting Ross this time because of what he calls her voting record while serving in the legislature of raising taxes and supporting “reckless government spending.”

“North Carolinians could pay billions more if Deborah Ross returns to office,” Bryson said in a statement. The national AFP group is backed by conservative billionaires Charles and David Koch.

Ross’ campaign said the assistance from Americans for Prosperity is another example of Burr getting help from special interests to try to win re-election.

“The Koch Brothers and Richard Burr are exactly what North Carolinians hate about Washington, and that’s why they’re ready for a change,” Ross spokesman Cole Leiter said in an email. Ross, meanwhile, has a record of helping working families keep more of what they’ve earned, Leiter added.

Later Tuesday a super PAC led by John Bolton, a former United Nations ambassador, said it would spend $1 million through the rest of the campaign on social media, satellite TV and elsewhere to support Burr’s re-election. Bolton, in a statement, cited Burr’s foreign policy credentials and his chairmanship of the Senate Intelligence Committee.

Burr also unveiled Tuesday a new television ad highlighting his work passing legislation designed to help people with disabilities accumulate funds without losing Social Security and Medicaid eligibility.