Nikki Haley on Monday blasted former President Trump's first public comments on the death of Russian opposition leader Alexei Navalny, slamming the GOP frontrunner's failure to condemn Russian President Vladimir Putin.

Why it matters: Trump's comments have renewed scrutiny from establishment Republicans on his foreign policy views, while highlighting the deepening ideological fault lines within the GOP when it comes to Russia.

• His reaction to Navalny's death has also intensified fears among Democrats and some Republicans of how a second Trump term could undermine the U.S. role in western alliances.

State of play: On Monday morning — three days after Navalny's death became public — Trump broke his silence on Truth Social, saying the death made him "more aware of what is happening in our Country [sic]."

• "It is a slow, steady progression, with CROOKED, Radical Left Politicians, Prosecutors, and Judges leading us down a path to destruction," he wrote.

What they're saying: Haley took to X Monday to say Trump could have condemned Putin "for being a murderous thug" or "praised Navalny's courage."

• "Instead, he stole a page from liberals' playbook, denouncing America and comparing our country to Russia," added Haley, former U.S. ambassador to the UN.

The big picture: Western political figures, including Haley and President Biden, have widely pinned Navalny's death in Russian custody on Putin, who has long been accused of violently retaliating against his critics.

• Before Trump's comments Monday, Haley appeared that morning on "Fox & Friends" to call Trump "weak in the knees" when it comes to dealing with Putin.

Meanwhile, former Rep. Liz Cheney (R-Wyo.) told CNN's "State of the Union" Sunday that Trump's silence underscored the threat his return to the White House would pose.

• "We have to take seriously the extent to which you've now got a Putin wing of the Republican Party," Cheney said.

Zoom out: During his presidency, Trump was criticized for being favorable to Putin.

• Last week, the former president encouraged Russia to do "whatever the hell they want" if a NATO nation were behind on its defense obligations.

Of note: Trump is current facing 91 criminal counts in four different jurisdictions. On Friday, he was ordered to pay a $354 million penalty in a New York civil fraud case that he claimed was politically motivated.

Go deeper: Alexei Navalny's widow says she will continue his Russian opposition work

Editor's note: This story has been updated with additional details throughout.