Regarding Joe: Why this weekend?

Since JD Vance was put on the ticket, the Biden campaign has been polling the four possibilities. They are doing this because the Democrats have and are good lawyers and they know Trump's goose is cooked. It will take convincing Melania of three things to get him out of the race: 

1. Once the DC Circuit Court receives the remand instructions from the Supremes, Judge Chutkin will quickly ask for briefs and make her decisions. Some of the memos analyzing the issues have likely been written already. The evidence (which Trump has from discovery) is such that he knows he is dead to rights on whatever she finds fits under the heading of unofficial acts.

2. She makes it clear that winning the election does not stop the trial. The meme is that it might. The meme is wrong.

3. The question of how to confine a former president is developed, with Trump getting some idea of what awaits him.

This is why the Biden-Harris campaign is polling Vance v. Biden and Vance v. Harris. Put Whitmer on the ticket with Harris and the Blue Wall is strong. Harris will bring back the Obama voters and take Republican women from Vance as well.

Polls are important, but the real question is whether Joe is in such decline as to need to resign now or have Harris and the Cabinet make the decision for him. If these discussions are not taking place, the members of the cabinet are not doing their jobs.

As to the polls, they went out as soon as Vance was selected and likely finished today. Tonight, they do the analysis and give it to Joe in Delaware over the weekend. The Democratic polls are better because they have a database of actual likely voters. Who is registered and how often they vote are matters of public record. You draw a random sample from that frame, mostly in the battlegrounds, and will get a very accurate answer. 

The GOP polls are not as good. They use random digit dialing. They have for decades - as long as I have been in politics. Their results oversample low information voters who will stay home - which is why any RDD poll that GOP pollsters do is off by 3 or four points. This is why RCP poll averages are trash.

Joe would likely win and the Dems will pick up the House because of redistricting away GOP gerrymanders and will keep the Senate because no one is giving money to GOP Senate candidates. Next year, the Senate needs to reduce cloture threshold from 60 to 56 so that real governance can happen, including going back to making deals to get things passed.

The polls are important, however the big question is whether he is declining now, rather than two years from now - which would cost the Democrats hugely in the midterms.