There at least 20 ways to look at the immediate effects of RBG's passing. I will only list a few:
1) Trump and Senate immediately (before election) appoint a new justice. Results = Pissed off Dems who will be more motivated to vote. Possibly some one-issue GOP voters who don't feel the motivation anymore, since they got that issue. I don't see how Dem votes would be lessened, or GOP votes on Nov 3 would be higher as a result.
2) Trump and Senate announce a prospect, but say they will wait until after election to appoint. I don't see this being much different than #1, because if everybody expects Trump's nominee to be approved anyways, what's the diff?
3) Trump and Senate promise (pinky swear) not to approve a nominee unless Trump wins re-election. Now, this could possibly earn more GOP votes among whoever is undecided or non-motivated, but would do the same for potential Dem voters. So, not much difference than #1 or #2, since also... nobody would believe Trump and McConnell wouldn't try to push a Justice through during the time between the election and Jan 20, even if Biden wins.
4) I think Senator McConnell will try to push through a Trump SCOTUS Nominee to replace RGB, but I think enough (4-5) GOP Senators will abstain or vote no on confirmation.
5-20) ... nothing is different. Dems and GOP all know the stakes of this election. We knew it before today, before RGB's passing. We also know that all it takes to increase the number of members of the Supreme Court is a basic majority in the House, plus 50 votes in the Senate, plus Biden's signature to enact that statute.
Congress has changed the number of judges on the Supreme Court many times in the history of the United States. The number of justices has gone up, and down. If the GOP Senate and McConnell want to openly disregard their own policy they made 4 years ago... when they said the people should vote for president first and that president should select the next Justice... then they will suffer the consequences.
We need to focus, more than ever, on electing Joe Biden as President and kicking Trump out of our house. Add the Senate, and we can preserve the legacy created by Ruth Bader Ginsberg.