RICHMOND, Va. — The federal government is again open for business, and Republicans in Washington are licking their wounds from the failed Tea Party attempt to derail President Obama’s health care overhaul. But here in Virginia’s capital, conservative activists are pursuing a hardball campaign as they chart an alternative path to undoing “Obamacare” — through the states.

One leading target is Emmett W. Hanger Jr., a Republican state senator from the deeply conservative Shenandoah Valley, who prides himself on “going against the grain.” As chairman of a commission weighing one of the thorniest issues in Virginia politics, whether to expand Medicaid under Mr. Obama’s Affordable Care Act, he is feeling heat from the Republican right.

His openness to expansion has aroused the ire of Americans for Prosperity, the conservative advocacy group backed by the billionaire industrialist brothers Charles and David Koch. Dressed in emerald green T-shirts bearing the slogan “Economic Freedom in Action!” its members are waging what the senator calls “an attempt to intimidate me” in Richmond and at home.

They have phoned his constituents, distributed leaflets and knocked on 2,000 doors in his rural district. When the Republican town committee met Monday night in Mr. Hanger’s home county, Augusta, Americans for Prosperity was there.