WASHINGTON (AP) — Sen. Jeff Flake of Arizona is warning in his farewell address that the "threats to our democracy from within and without are real."

Flake is perhaps the most vocal Republican critic of President Donald Trump in the Senate. While Flake did not mention Trump in his speech Thursday, he said that describing the state of the nation's politics as "not healthy is something of an understatement."

Flake also warned about global events, saying that Russia's President Vladimir Putin (POO'-tihn) is determined to hijack democracies. He said the U.S. should recognize that, as "authoritarianism reasserts itself in country after country that we are by no means immune."

Flake declined to seek re-election to a second term, acknowledging his battles with Trump made it unlikely that he could survive a primary challenge.