President Joe Biden's biggest primary rival in 2020, Sen. Bernie Sanders (I-VT), just endorsed his 2024 re-election bid and said he won't run against him for the Democratic nomination.
“The last thing this country needs is a Donald Trump or some other right-wing demagogue who is going to try to undermine American democracy or take away a woman’s right to choose, or not address the crisis of gun violence, or racism, sexism or homophobia,” Sanders said in an interview. “So, I’m in to do what I can to make sure that the president is reelected.”
Sanders is just a touch older than Biden at 81 and used to be to Biden's left politically.
After two-plus years of seeing Biden's policies, however, Sanders probably realizes that he's getting just about everything that he wants from Biden and his Democrat allies.
The party has seen a radical leftward shift since the 2020 campaign, when Biden ran as the more moderate candidate.
There's really no reason for Sanders to run at this point, so he might as well enjoy his relatively easier gig as a Senator.