WASHINGTON — Saying their patience is at an end, conservative activist groups backed by the billionaire Koch brothers and other powerful interests on the right are mobilizing to pressure Republicans to fulfill their promise to swiftly repeal the Affordable Care Act.

Their message is blunt and unforgiving, with the goal of reawakening some of the most extensive conservative grass-roots networks in the country. It is a reminder that even as Republicans control both the White House and Congress for the first time in a decade, the party’s activist wing remains restless and will not go along passively for the sake of party unity.

With angry constituents storming town hall-style meetings across the country and demanding that Congress not repeal the law, these new campaigns are a sign of a growing concern on the right that lawmakers might buckle to the pressure.

“We’ve been patient this year, but it is past time to act and to act decisively,” said Tim Phillips, the president of Americans for Prosperity, which is coordinating the push with other groups across the Kochs’ political network. “Our network has spent more money, more time and more years fighting Obamacare than anything else. And now with the finish line in sight, we cannot allow some folks to pull up and give up.”