President Trump snuck in a dig at GOP Senator Jeff Flake, calling him "weak" on crime and border security, while thanking Phoenix for the "amazing" crowd that came out to watch his speech last night.

This isn't the first time Trump has gone after Flake on Twitter. Last week, Trump tweeted that he was "toxic" and signaled his support for Flake's opponent in the 2018 Senate race, Dr. Kelli Ward.

The Trump-Flake ongoing feud initially began when Flake openly opposed Trump during his presidential campaign. He also sharply criticized Trump and condemned the Republican Party for enabling Trump's rise to the presidency in his book, "The Conscience of a Conservative." Trump's recent flurry of tweets attacking Flake is the president's way of retaliating.