It will be interpreted as Republicans shutting down the government... again. Moderates and Independents, and Centrists on both sides tend to strongly dislike that, and it could swing the election to a Democrat victory.
No it won't. The Supreme Court will function just fine with one open seat. Ties affirm whatever the lower court decided. Whole Supreme Court terms have elapsed, within the last 50 years, with empty seats.
I think it's far easier to sell the argument that the voters should decide on who gets to nominate a replacement for Scalia, than that we should shut down national parks or whatever. These aren't remotely the same type of "shutdown".
That might be the case, but stalling a justice nomination isn't as severe or visible as a government shutdown and might not get the same level of attention.
