[Here’s what you need to know about the Alabama, Texas and Maine primary elections.]

President Trump on Tuesday night endorsed Tommy Tuberville, the former college football coach who won the most votes in last week’s Republican primary for the Senate seat from Alabama and is locked in a runoff against Jeff Sessions, the former attorney general.

The endorsement came after Mr. Trump agreed to sit on the sidelines during the crowded primary, which had become a show of which candidate displayed more fealty to the president. Mr. Tuberville received the most votes, and polls show him with a comfortable lead heading into the runoff against Mr. Sessions, which is scheduled for March 31.

“Tommy was a terrific head football coach at Auburn University,” Mr. Trump wrote on Twitter. “He is a REAL LEADER who will never let MAGA/KAG, or our Country, down! Tommy will protect your Second Amendment (which is under siege), is strong on Crime and the Border, and truly LOVES our Military and our Vets. He will be a great Senator for the people of Alabama. Coach Tommy Tuberville, a winner, has my Complete and Total Endorsement. I love Alabama!”

The endorsement had been a possibility since the end of the primary, during which Mr. Trump had agreed to requests from some Republicans to stay on the sidelines. His reward was being able to criticize Mr. Sessions once it was over — something he did the day after the primary took place.