Joe Biden and the ‘Convention Bounce’

With President Trump in office, polarization has only deepened: Public opinion of his performance has been markedly stable throughout his term, and most Americans report feeling strongly about him one way or the other, according to polls. Even among independents, his approval rating has hardly climbed higher than the low 40s.

“Historically the conventions have been a time for the party to unify,” Kyle Kondik, the managing editor of Sabato’s Crystal Ball at the University of Virginia Center for Politics, said in an interview. “But the bottom line is that there are not that many undecideds, and the conventions don’t really need to unify the party because the parties are already unified.” He pointed to an average that he had calculated using four high-quality national polls taken just before the D.N.C., showing that more than nine in 10 members of each major party said they would support their nominee.

Then again, it’s not all about the horse race. Polls show that supporters of Joseph R. Biden Jr. are overwhelmingly likely to say they’re casting their ballot mostly to oust Mr. Trump, not because they’re particularly eager to put Mr. Biden in the Oval Office. The Democratic nominee’s favorability rating currently runs about five points lower than the share of registered voters who say they plan to vote for him in the fall, according to averages from RealClearPolitics.

This isn’t exactly a fatal flaw — but it’s enough to cause Mr. Biden’s campaign some concern. If all the pro-Biden messaging at the convention failed to give him a bounce in head-to-head matchups against Trump, but nevertheless brought his favorability rating up, that could offer him a new sense of security.

Mr. Biden has remained something of a candidate-in-waiting since the pandemic began and he became the Democrats’ presumptive nominee. That’s partly by choice: Widely known as an uneven campaigner, the former vice president has seemed content to mostly stand aside as Mr. Trump publicly struggled to contain the coronavirus crisis or stem the economic downturn.

The convention was supposed to be Mr. Biden’s moment to turn on his campaign, addressing his largest audience yet after days of runway programming to boost his momentum. But then the pandemic got in the way.

The Democrats canceled their plans for a large in-person gathering in Milwaukee, dampening anticipation in the run-up to the event. This also significantly altered the vibe of the broadcast itself, making it feel less like a live event and, at times, more like a telethon.