Biden is going to win out imo unless someone steps up.
In August 2003, dikk Gephardt led most democrat presidential polling. Howard Dean was in second place before becoming the front runner. Kerry was regularly in third or fourth place.
In August 2007, Hillary was leading Obama by nearly 20 points in most democrat polling, and was also significantly ahead of John Edwards (who ultimately beat her in Iowa too).
In August 2007, Rudy Giuliani was the runaway leader in republican polling. McCain was in third or fourth place, depending on the poll.
In August 2011, Rick Perry led Mitt Romney in most republican polling.
In August 2015, Trump led most republican presidential polling.
In August 2015, Hillary led most democrat presidential polling (but to be fair, she ran virtually unopposed)
Notice how most of the early presidential leaders had high name ID. Hillary, Rudy, Trump, even Perry...were all major figures. Biden fits that mold as a former VP. The more people know you, the more people who will blindly name you when asked who they support. Biden's support has been falling in most polls since the debates, and two bad debates aren't going to help him.
He's going to keep fumbling and keep looking frail. He's not campaigning in most states. He's barely in Iowa. Remember, Iowa is notoriously hard to poll on the democrat side due to the rules. It's way too early to declare anyone is going to win. The only person I see who keeps gaining in the polls is Warren.