HUNTSVILLE, Ala. (AP) — U.S. Rep. Mo Brooks, a conservative firebrand and staunch supporter of former President Donald Trump who has come under fire for remarks he made preceding the attack on the U.S. Capitol, joined the Alabama GOP primary field on Monday to replace Sen. Richard Shelby.

The north Alabama Republican announced his entry into the race at an event with former Trump adviser Stephen Miller. He joins former Trump ambassador Lynda Blanchard in a Republican primary field that is expected to attract a number of other hopefuls.

Miller was an influential force in pushing Trump’s efforts to curb immigration. He engineered the former president’s Muslim travel ban and was widely viewed as the driving force behind the Trump administration’s hardest-line immigration policies.

“Nobody has had President Trump’s back more over the last four years than Mo Brooks. Now I need you to have his back,” Miller said as he introduced Brooks.

Brooks, 66, has come under fire for telling the rally that preceded the Capitol riot that it was time to “start taking down names and kicking ass.” Brooks said the phrase was intended to fire up the crowd for the next election cycle and is being misconstrued as advocating the violence that followed.

Shelby announced earlier this year that he would not seek reelection in 2022, igniting what is expected to be a messy GOP primary at a time when the national Republican Party is trying to chart a direction following Trump’s departure.

Brooks has served five terms in the House, where the former prosecutor joined the conservative Freedom Caucus. He serves on the Armed Services Committee and Science, Space, and Technology, two important committees for his north Alabama district.

Republicans hopefuls in a state where Trump won 62% of the vote are expected to try to convince primary voters they are the rightful banner carriers for the Trump agenda. But some observers worry the race could crown a far-right nominee to replace one of the Senate’s most senior leaders with a deep establishment ties.

Republican former Rep. Bradley Byrne of Alabama said the winner of the GOP primary will likely be whoever can convince voters they are the best heir to Trump and his “Make America Great Again” agenda.

“They are going to be very conservative. They are going to be the most genuine, most effective carrier of the Trump/MAGA flame,” Byrne said.

David Mowery, an Alabama-based political consultant, said support for Trump is “the table stakes” — a requirement to get in the game for Republicans seeking office in Alabama. However, Mowery said he thinks there is trepidation among establishment Republicans.

While Shelby amassed a far-right conservative voting record, he never embraced the bombastic, populist style that has propelled Republicans like Georgia Rep. Marjorie Taylor Greene.

“I think people are worried that you are going to get someone that’s more concerned about throwing bombs and seeing their name in the paper then you are somebody who does what Shelby does and that is bring home the bacon and make sure Alabama is taken care of in every spending bill,” Mowery said.

Others sometimes mentioned as potential candidates are Alabama Secretary of State John Merrill and Shelby’s former chief of staff, Katie Boyd Britt, who now heads an influential business lobby.

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