This from Rasmussen.

"The new survey finds Trump with 74% of the Republican vote. Biden has the support of 79% of Democrats. Among voters not affiliated with either major party, itís Biden 48%, Trump 36%."

Going by history, the percentage of Republicans and of Democrats who are saying they'll vote for their candidate is very low. By November, those percentages will be up to their historical average of 90%. But what stands out is the independents, the non-affiliated voters as Rasmussen puts it. 48-36% in favor of Biden. The basement strategy for Biden while letting Trump be Trump is working just fine, especially among independents, swing voters, the non-affiliated. Don't interrupt or stop you opponent when he's going down hill. Let him go.

89% of Democrats voted for Hillary in 2016, 92% for Obama in 2012. 89% for Obama in 2008, 89% for Kerry in 2004, 87% for Gore in 2000.
88% of Republicans voted for Trump in 2016, 93% for Romney in 2012, 90% for McCain in 2008, 93% for Bush 2004, 91% for Bush in 2000.

I'll stop there as Perot, a well financed third party candidate drew plenty of votes from both parties in 1992 and 1996. So you can see the historical average of roughly 90% of the two major parties voting for their candidates. I don't expect that to change in 2020.
It's high past time that we start electing Americans to congress and the presidency who put America first instead of their political party. For way too long we have been electing Republicans and Democrats who happen to be Americans instead of Americans who happen to be Republicans and Democrats.