WASHINGTON (AP) — Former President Donald Trump has endorsed the Republican opponent of a Virginia congressman who leads the hard-right House Freedom Caucus in what could be a defining moment in the GOP primary set for June 18.

The endorsement of John McGuire, a state senator, provides a jolt of momentum for the challenger and could be difficult for the incumbent, two-term Rep. Bob Good, to overcome. The primary is one of the most closely watched in the nation as millions of dollars pour into the race from various Republican-aligned groups.

Trump said that McGuire, 55, "has my Complete and Total Endorsement! MAGA2024." Meanwhile, he calls Good bad for Virginia and bad for the USA. In the endorsement, posted on Truth Social, Trump said Good was constantly attacking and fighting him until recently when he gave a "warm and 'loving' Endorsement - But really, it was too late. The damage has been done."

The two candidates have sought to show their allegiance to Trump in the solidly Republican district, but Good, 58, initially backed Ron DeSantis in the GOP presidential primary, before endorsing Trump. The former president did not forget and took revenge three weeks before primary day, saying of Good, "he turned his back on our incredible movement."

McGuire has sought to underscore his loyalty to Trump throughout the campaign to mark a contrast between the two candidates, who have similar stances on many political issues.

"Thank you to President Donald J. Trump for endorsing my campaign for Congress!," McGuire said in a statement. "I've been with Trump since he came down the escalator and when I'm in Congress, I'll back his agenda and put America First!"

Good was among the parade of GOP lawmakers and allies who have appeared with Trump at his New York City trial as a sign of support. Both he and McGuire accompanied Trump the same day. "We're here to have his back," Good said of the trip.

But McGuire said Trump was right about Good and that he cannot be trusted.

"Trump has recognized that I'm the 100% MAGA candidate in this race and I appreciate it," McGuire said.

Good's campaign did not immediately respond to a request for comment.

Good is a fiscal conservative who has pushed for deep spending cuts and was one of eight Republican lawmakers who voted with Democrats to oust then-speaker Kevin McCarthy. The fallout from that vote is also evident in the congressional race as groups sympathetic to the former speaker spend heavily to defeat Good while others have come to his defense.