As part of its state-by-state effort to dismantle the Affordable Care Act, a group backed by billionaire conservative benefactors Charles and David Koch is going after a Republican lawmaker in Virginia who has signaled an openness to the law’s Medicaid expansion.

An article published Saturday in The New York Times details how the conservative advocacy group Americans for Prosperity is employing a grassroots campaign to pressure state lawmakers to reject the Medicaid expansion under the health care law.

The group is currently going all out in Virginia, where this year’s gubernatorial race pits a Democrat who favors expansion (Terry McAuliffe) against a Republican who opposes (Ken Cuccinelli). It’s also targeting Republican state Sen. Emmett W. Hanger Jr., who is considering signing off on the expansion.

“This has been one of those trench warfare kind of efforts for a year now, and I think it is one of those hidden stories of the whole fight against Obamacare,” Tim Phillips, president of Americans for Prosperity, told the Times. “It’s not flashy; it’s just in a whole bunch of state capitals and in the districts of a whole lot of state legislators, but it’s such a crucial aspect of the overall long-term effort to roll back Obamacare.”

The same group, supported by the Koch brothers, launched a television ad campaign earlier this year in Virginia and Ohio warning about the “true” effects of the Affordable Care Act. And the Kochs are tied to another conservative group, Generation Opportunity, behind the viral web video that featured a “creepy” Uncle Sam and urged young people to avoid Obamacare’s health exchanges.

This post has been updated.