Trump on Biden's withdrawal: "Crooked Joe Biden was not fit to run"

• "He only attained the position of President by lies, Fake News, and not leaving his Basement," Trump wrote. "All those around him, including his Doctor and the Media, knew that he wasn't capable of being President, and he wasn't."

What's next: Trump will now likely pivot his campaign — and attacks — to focus on Vice President Kamala Harris, whom Biden endorsed to take his place.

• Donald Trump Jr. displayed that shift, reacting on X, "Kamala Harris owns the entire leftwing policy record of Joe Biden."
• The GOP nominee's son continued: "The only difference is that she is even more liberal and less competent than Joe, which is really saying something."

State of play: Sen. J.D. Vance (R-Ohio), whom Trump announced as his running mate Monday, was set to face off against Harris, VP versus VP.

• "Joe Biden has been the worst President in my lifetime and Kamala Harris has been right there with him every step of the way," Vance wrote on X Sunday.

• Echoing an ad released by pro-Trump Super PAC MAGA Inc. shortly after Biden announced his withdrawal, he continued, "She owns all of these failures, and she lied for nearly four years about Biden's mental capacity — saddling the nation with a president who can't do the job."

Go deeper: BIDEN DROPS OUT OF RACE, ENDORSES HARRIS IN STUNNING SHIFT FOR 2024 ELECTION

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