Donald Trump announced he will travel to Alabama next weekend to stump for Sen. Luther Strange as he tries to retain Attorney General Jeff Sessions’ Senate seat in what’s turning out to be a messy inter-party fight in one of the America’s most conservative states. Strange, who was the Alabama state attorney general until earlier this year when he was appointed to the U.S. Senate, is struggling to keep up with challenger and former Chief Justice of the Alabama Supreme Court Roy Moore in the Sept. 26th runoff.

The race has split the Republican Party along establishment and insurgent lines. National Republican leaders worry a Moore victory could portend a wave of primary challengers in 2018, in what looks to be a challenging cycle for the GOP already. Trump has been supportive of Strange, as has his on-again-off-again nemisis Majority Leader Mitch McConnell, as well as the Republican establishment. Steve Bannon has backed Moore, pushing his candidacy as the latest front in a populist “midterm war” on the Republican establishment. Former Alaska Gov. Sarah Palin is also expected to be in Alabama supporting Moore before voters go to the polls.

Polling shows that the vast majority of Republican voters in Alabama remain enamored with President Trump with his approval ratings hovering above 80 percent. The two remaining candidates, however, have divided opinion. Polling has been a bit all over the map, and while the race appears to have tightened, Strange has struggled to keep up with the recalcitrant former judge, who has consistently led in head-to-head polls, sometimes by double digits.

The evangelical Moore has attracted anti-establishment types after he shot to national notoriety for his refusal to remove a statue of the Ten Commandments from the state Supreme Court building and his order not to issue same-sex marriage licenses even after the Supreme Court ruled forbidding gay marriage unconstitutional. Moore handily won the Aug. 15th special election with 39 percent of the vote to Strange’s 33 percent, but was unable to reach the 50 percent threshold to avoid a runoff. Alabama congressman Mo Brooks received a significant 20 percent of the vote, but was eliminated from the two-candidate runoff later this month. Brooks, a member of the House Freedom Caucus, endorsed Moore on Saturday.