RCP average now has Biden at 32%, back to pre-debate level
for the week or so prior to the June debate, and higher than at any point before his announcement (going back through January 30 -- he was leading then despite not having announced yet, with most Dems assuming he would run).
https://www.realclearpolitics.com/epolls/2020/president/us/2020_democratic_presidential_nomination-6730.html
He's still quite a ways from his RCP polling peak of 41.4%. But he was polling between 32% and 35% from May 23 through June 29 (that's a couple of days after the debate, but that was when it began to affect the polls).
RCP has his current lead over the other candidates at +15.8. That's a significant lead in a field with so many candidates, and three other major candidates polling above single digits.
Biden at 32% currently has more support than Sanders (16.2%) and Warren (14.0%) combined. Harris's current RCP average is 10.5%, less than a third of Biden's support.
Buttigieg is at 5.7%, O'Rourke at 2.8%, Yang at 2%, Booker at 1.5%, Klobuchar at 1.2%, Steyer at 1.0%, Castro at 1.0%, Gabbard at 0.8%, and de Blasio at 0.7%.