President Donald Trump appeared Thursday to endorse Sen. Jeff Flake’s primary opponent, lashing out at the Arizona Republican senator who has become one of his most vocal critics.

Trump’s attack on Flake was his second Twitter strike of the morning on a GOP senator and followed a social media strike on South Carolina’s Lindsey Graham. The two broadsides on two moderate members of his own party’s Senate caucus illustrated anew how the president repeatedly courts the party’s conservative members who are more in line with his own political base.

The president, defacto leader of the Republican Party, tweeted he believes it is “great to see” Ward, a former state senator, is running to unseat Flake. He wrote that Flake is “WEAK on borders, crime and a non-factor in Senate. He’s toxic!”

Great to see that Dr. Kelli Ward is running against Flake Jeff Flake, who is WEAK on borders, crime and a non-factor in Senate. He’s toxic!

— Donald J. Trump (@realDonaldTrump) August 17, 2017

Notably, Ward’s campaign is being funded, in part, by Trump supporters.

In his new book “Conscience of a Conservative,” Flake described the GOP’s forced marriage with Trump as a “Faustian bargain.”

Flake wrote that he sees in Trump a “strange specter of an American president’s seeming affection for strongmen and authoritarians.”

[Flake Reflects on the Rise of Trump in New Book]

The GOP senator took his Trump criticism on a television book tour, and did not hold back in letting show his true feelings about Trump and his political movement.

“The party has lost its way. We’ve given in to nativism and protectionism,” he told CBS on July 30. “And I think that if we’re going to be a governing party in the future and a majority party we’ve got to go back to traditional conservatism.”

And following Trump’s Tuesday press conference during which he appeared to walk back a total denunciation of white supremacist groups, Flake criticized the remarks.

“We can’t claim to be the party of Lincoln if we equivocate in condemning white supremacy,” Flake tweeted on Wednesday. And hours after Trump’s Tuesday remarks, Flake tweeted leaders “can’t accept excuses for white supremacy & acts of domestic terrorism.

“We must condemn,” wrote Flake, though he did not use Trump’s name nor tag his Twitter handle. “Period.”

We can’t claim to be the party of Lincoln if we equivocate in condemning white supremacy

— Jeff Flake (@JeffFlake) August 16, 2017

We can’t accept excuses for white supremacy & acts of domestic terrorism. We must condemn. Period.

— Jeff Flake (@JeffFlake) August 15, 2017