Tea Party leader Ted Stevenot plans to challenge Ohio’s Republican Gov. John Kasich for the Republican gubernatorial nomination this year.

Stevenot, 48, will announce his candidacy with running mate Brenda Mack, 56, on Tuesday, according to a press release. Stevenot is the president of the Ohio Liberty Coalition and a co-founder of the Clermont County tea party.

A primary challenge could muddy Kasich’s already shaky base, just as Democrats line up to try and unseat the Republican from the top state office. State Democrats are supporting state official Ed FitzGerald’s challenge. Another Democrat, Todd Portune, also announced his intentions to run earlier this week.

It’s the latest shot fired in the GOP’s civil war, with tea party candidates slamming established Republicans with primary challenges and records the far-right deems too liberal.

In Kasich’s case, he’s under fire for accepting $2.5 billion in federal money to expand the state’s Medicaid—a move made possible by the president’s health care reform law the Republican Party hates so much.

The Medicaid expansion had little support in Ohio’s Republican legislature, so Kasich pushed it through with a vote from the state’s Controlling Board—a move later upheld by the state’s Supreme Court. It could curb uninsurance in the state by up to 60% and extend insurance benefits to an estimated 275,000 poor Ohioans.

Kasich’s approval rating rose following the Medidcaid expansion and launch of Obamacare, according to a December poll by Quinnipiac University, but just 36% of respondents said they thought he should be reelected.

If Stevenot and Mack gather the required 1000 signatures by next month, Kasich will be the first sitting Ohio governor to face a primary challenge in 36 years.