Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

WASHINGTON — The most endangered Republican in the Senate will now have to fend off a primary challenger before attempting to win back his seat in one of the most important contests of the 2018 midterm elections.

Danny Tarkanian, a conservative businessman and perennial candidate, announced Wednesday that he plans to challenge Sen. Dean Heller, R-Nev.

Sen. Dean Heller, R-Nev., center, is surrounded by media on his way to view the details of a new health care bill on July 13, 2017. Alex Wong / Getty Images file

Heller charted a meandering course through the Affordable Care Act repeal debate, leading Tarkanian to say the senator had “turned his back on us.” Heller stridently opposed an early version of the GOP health care plan before voting for the final bill in the Senate.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

“I am a conservative Republican who supports the policies of President Trump to repeal Obamacare and end illegal immigration. I will continue to support President Trump's policies that have led to a 20% increase in the stock market in just six months,” Tarkanian said in a statement announcing his candidacy.

Heller’s camp quickly fired back, noting Tarkanian’s electoral record is 0-5.

“Danny Tarkanian is a perennial candidate who has spent millions of dollars on five campaigns over the last decade. Nevada voters have rejected him every time,” Heller spokesman Tommy Ferraro said in a statement. “He’s wasted conservatives’ time and cost the Republican Party seats up and down the ballot. If he ultimately files for U.S. Senate he will lose in the primary.”

Tarkanian, son of college basketball coach Jerry Tarkanian, most recently lost a 2016 challenge to Rep. Jacky Rosen, D-Nev., the Democrat running against Heller next year.

Still, Tarkanian’s multiple campaigns, while unsuccessful, have made him a well-known name in Nevada politics. If nothing else, his presence in the race could force Heller to divert resources and push the senator into more conservative positions than might be advisable in the Democratic-leaning state.

Heller, the only Republican senator from a state Hillary Clinton won last year, is already Democrats’ top target in upper chamber in a year that otherwise has them on defense. Groups opposed to Republican attempts to repeal Obamacare spent more than $15 million on ads hitting 13 GOP senators during the health care debate. More than third of those ads — $5.6. million — targeted Heller alone.