Biden is not up for reelection. He doesn't need to energize his base because Democrats don't take all their cues from one leader like Republicans tend to do, especially so now as cult exists around one man.
It's so funny that Republicans tried to claim that Democrats had done the same thing with Obama, and in hindsight such ideas are hilariously projective based on the last 7 years.
As I mentioned above, Democrats up until now are largely running away from Biden, and due to the Trumpist base's obsession with his anointees have suddenly seen polling shift against GOP control of both houses toward the likelihood that Democrats will increase their majority in the Senate by at least 2, all due to the predilections of Trump-anointed candidates defeating far more mainstream conservatives.
Here's reality for you: Elected Democrats have been critical of Biden on various policies for the entirety of his presidency, so there is no need for them to take different positions just because the election is near. So Biden's stewardship of the White House has already been untied from most Democratic candidates, while nearly all of them have supported Biden whenever his actually successful policies have come up for votes - the times Manchin and Sinema or McConnell's filibuster allow them to.
So to my sensibilities, Democrats running this fall have a tremendous tailwind at their backs coming from multiple sources. Roe/women's autonomy - obviously, record employment numbers, the decline in Covid's impact - though that can still change at any moment due to unknown variants, unquestioned support for a free Ukraine - unlike many in the GOP who openly back Russia and Putin, and the unmistakable embrace of white supremacy, racism, sexism, and history denial by those now considered in the mainstream of the Republican Party as exemplified by CPAC this past week.
All in all the Dems are in a much better place than they thought they'd be as little as 90 days ago. And most of the reasons why are because of GOP extremism manifesting itself all over the country and the unmistakable recent successes of Biden's stewardship that are simply undeniable.