Barry Moore

Representative Barry Moore of Alabama, a third-term congressman and longtime loyalist of President Trump, faces Jared Hudson in his state’s Republican Senate primary runoff on Tuesday.

Here are five things to know about Mr. Moore, 59, of Enterprise, Ala., who led by about 14 percentage points in the May primary for the seat that the Republican senator Tommy Tuberville is vacating.

1. He was an early endorser of Mr. Trump’s first campaign for president. Mr. Moore endorsed Mr. Trump at a rally in Mobile, Ala., in August 2015, two months after he entered the race. Mr. Moore, then a state lawmaker, told the crowd that he was impressed by Mr. Trump’s performance at a Republican presidential debate. “I saw a man that understood small business,” Mr. Moore said, adding, “I saw a man that loved this country.” Mr. Trump recalled that support when he endorsed Mr. Moore’s candidacy for Senate, saying on social media that the representative had “been with me from the very beginning.”