Ahead of a Tuesday Republican runoff, President Donald Trump is fully inserting himself in a U.S. Senate race in Alabama, holding a rally Friday night for Sen. Luther Strange (R-AL), who faces a spirited challenge from former Alabama Supreme Court Justice Roy Moore, in a race that has strained GOP alliances in the Yellowhammer State.

The President will stop tonight in Huntsville, Alabama - not far from there, Mr. Trump had a gigantic rally back in late February of 2016, as he drew some 30,000 people to a football stadium in Madison.

"I am supporting "Big" Luther Strange because he was so loyal and helpful to me!" Trump wrote in one of a number of tweets about the Alabama race.

Behind in the polls, Strange used a Thursday night debate with Moore to repeatedly remind Alabama voters who the President was supporting.

"The first question is, who does the President support? The President supports me," Strange said.

As for Moore, he has drawn support from a number of conservative Republicans, but now finds himself pitted against someone who has the backing of the President, something that Strange mentioned several times at a debate on Thursday night.

"This race is not me against the President," Moore said.

Moore would seem to be a perfect ally for the President - someone who rails against the GOP Establishment, focusing much of his ire on Senate Majority Leader Mitch McConnell - but Mr. Trump has stuck with "Big Luther," who has trailed in the polls leading up to the runoff.

"If they believe in Trump’s agenda - Moore is the clear choice," said Rep. Steve King (R-IA), "but if they follow the cult of personality - then Strange."

Strange was appointed earlier this year to fill the seat of Jeff Sessions, who left the Senate to become U.S. Attorney General - Sessions was the first Senator to support Mr. Trump, but that has not earned him any loyalty from the President, who has castigated Sessions repeatedly.

While the President has backed Strange, Moore has received the backing of Rep. Mo Brooks (R-AL), who ran third in the original primary.

But the big voice on Friday will be that of President Trump, who has certainly been putting his political capital on the line for Strange.