WASHINGTON (AP) — Kentucky Sen. Rand Paul said Sunday that he won’t back GOP congresswoman Liz Cheney and her support for “endless wars” if she decides to run for the Senate from Wyoming.

Paul confirmed on CNN that he’s supporting Republican Cynthia Lummis, a former House member. Cheney, meanwhile, doubled down on her contention that Paul’s push to downscale U.S. military actions “blames America first” and ends up supporting terrorists. She spoke on NBC.

It was the latest round of rhetorical warfare between the pair, each a scion of a Republican political family. But it’s more than bickering members of Congress. The two are increasingly seen as the faces of GOP factions clashing over U.S. policy in Afghanistan and more broadly, the world. Like other Republicans, they’re claiming to be closer to President Donald Trump on foreign policy, even though his abrupt reversals and changes leave the administration’s direction unclear.

Paul has long tried to persuade Trump to trust his “America First” instincts and downscale U.S. military actions in places like Afghanistan and Syria. But others with Trump’s ear, including South Carolina Sen. Lindsey Graham, have counseled a more traditional GOP approach to foreign affairs. With Trump ousting hard-line national security adviser John Bolton last week — a firing Paul celebrated — more hawkish lawmakers are concerned about what comes next, particularly on Iran, where Trump seems eager to deal.

Since Wednesday, Paul and Cheney have been feuding on Twitter over who supports Trump more.