With 18% undecided or third-party, it appears that the pollsters didn’t push the respondents very hard for a choice. In the other polls that were showing double digits leads for Biden and few undecideds, I’m guessing a lot of the Biden support is very soft and can easily swing back to Trump by fall. Being the invisible candidate, Joe Biden is like a generic Democrat vessel who people assign any view that they want. That will change when Biden has to leave his basement and communicate and defend a vision for the country.
Often polls ask leading questions which force the subject to make a logical conclusion, an outcome that the pollster sought from the beginning. Are you in favor of abortion? Yes. Did you know that Biden is in favor of abortion? Didn’t know that. Are you in favor of Biden? Yes.