This could be by August 1st – two weeks before the convention
This is how the Hill is reporting statement’s from the campaign:
Former Vice President Joe Biden says he hopes to decide on a running mate by Aug. 1, about two weeks before the Democratic nominating convention in Milwaukee. Speaking at a digital fundraiser hosted by former South Bend, Ind., Mayor Pete Buttigieg, Biden said his campaign’s vice presidential committee has already interviewed the contenders on his shortlist. “We’re in the process of deciding the basic cut — about whether or not they really want it,” Biden said. “Are they comfortable? They’ve asked a lot of questions.”
The timing is quite a bit earlier than normal. Generally the presumptive nominee makes the announcement three or four days before the party convention.
My guess is that they want a VP choice in place earlier so there’s another campaigning voice focused on beating Trump and perhaps getting more attention and big speaking engagements than is normal. Part of this, I wonder, could be down to Biden’s apparently frail health – he is of course a 77 year old. In one of his few appearances during lockdown we had another of Biden’s famous gaffes which must be a concern for those running his effort.
You can envisage the campaign deciding to limit the possibility of more gaffes by having the VP nominee fronting the campaign a lot more.
There’s little doubt that the Trump campaign’s messaging will all be seeking to raise doubts about Biden’s health and mental capacity by using some of his widely publicised gaffes to underline the point.
Of the top three in the betting for VP nominee my money for now is on Warren who has had close political links with ‘Biden since WH2016 when there was an abortive plan for the two to share a ticket to stop Hillary. Although they are from separate parts of the party they clearly trust each other. Also Biden looks an old 77 while Warren a young 70 year old.