President Donald Trump announced Saturday that he plans to campaign next week for Sen. Luther Strange (R-Ala.), who is involved in a primary runoff against former Alabama Supreme Court chief justice Roy Moore.

I will be in Huntsville, Alabama, on Saturday night to support Luther Strange for Senate. "Big Luther" is a great guy who gets things done! — Donald J. Trump (@realDonaldTrump) September 16, 2017

The announcement sets up a showdown between the president and Steve Bannon, as the former White House chief strategist supports Moore.

Bannon left the administration earlier this month and rejoined Breitbart News, the site espousing white nationalist views that he led before joining Trump’s president campaign. The controversial former Trump aide is said to be targeting a number of incumbent GOP senators during the 2018 midterm elections. He has been careful, however, not to frame his efforts as a battle against Trump, but rather as one against establishment Republicans and the “swamp” in Washington.

Trump’s announcement came just hours after Rep. Mo Brooks (R-Ala.), who finished third in the first-round primary with 20 percent of the vote, endorsed Moore. In his announcement, Brooks called the race “an epic battle between the people of Alabama who put America first, and the Washington Swamp.”

Bannon’s allies are also portraying the race as an opportunity for Trump voters in the state ― of which there are many ― to reassert themselves in the wake of what they see as several key failures by the president to act on his agenda.

“Essentially, what the Alabama race provides for the first time since Trump began backtracking on a number of his core agenda items, is a chance for voters to affirm whether they believe in Trump or whether they believe in the agenda he campaigned on,” Breitbart News’ Matt Boyle wrote Saturday, citing news of Trump’s policies on immigration, climate change and the war in Afghanistan.

“If they believe in Trump’s agenda, Moore is the clear choice ― but if they follow the cult of personality around Trump, then Strange is the clear choice. And for Trump’s personality to rescue the endangered Strange campaign, it will take a herculean effort on the part of the president,” he added.

Moore, a staunch evangelical, would become one of the most hardline conservative senators if elected. Earlier this year, he suggested that the Sept. 11, 2001, terrorist attacks might have happened because the country had distanced itself from God.

The GOP primary runoff election will be held Sept. 26.