The 2008 vice presidential nominee Sarah Palin endorsed "conservative outsider" Danny Tarkanian in the Republican primary against incumbent Sen. Dean Heller, R-Nev.

"Danny Tarkanian is a conservative outsider who will support the 'America First' policies our nation needs to survive and thrive, including building the border wall, ending sanctuary cities, and finally repealing Obamacare. Common sense Conservatives in Nevada and across America need to unite and help win this critical fight," Palin said in a statement Thursday. "I strongly endorse Danny Tarkanian for the United States Senate and look forward to helping him win this important election."

Tarkanian expressed his thanks to Palin, while promising retribution for Heller's history of undermining President Trump and his agenda.

"I thank Government Palin for her endorsement and appreciate the confidence she has shown in our campaign. I will hold Dean Heller accountable for turning his back on Nevadans by voting against the repeal of Obamacare and helping Hillary Clinton win Nevada by attacking Donald Trump over and over again," Tarkanian responded.

Nevada is the only state with an incumbent GOP senator up for re-election in the 2018 midterm that Hillary Clinton won in the 2016 presidential election.

Heller and Tarkanian are the only two declared GOP candidates, but the Democratic side has four people vying for the nominee: former Las Vegas fire captain Jay Craddock, businessman Sujeet Narendra Mahendra, U.S. Rep. Jacky Rosen, and attorney Jesse Sbaih.

Heller is a first-term senator who is considered a centrist in the Republican Party.