Even if all that happens, it will very likely still be late for the election. It's not like you hit a switch and the economy is back to normal. And it won't revive people either.
Obviously I hope we will get a vaccine as soon as possible.
Politics is never about actually getting results. It's about looking like you're getting results. And the two most effective techniques for getting people to vote are to 1) engender feelings of hostility toward the other side (like Trump often does) or 2) give people hope, even false hope (like Obama did). If I'm his campaign manager, I choose this time for hope. The second Trump forces the FDA to issue approval for whatever vaccine he chooses first, his campaign will probably dump $100-million plus into primetime television commercials heralding the arrival of "his" vaccine "under his tremendous leadership," with soaring, triumphant orchestration soundtrack music and clips of nurses and healthcare staff and old ladies smiling and laughing while getting injections, and finally Trump declaring that we're "about to defeat the virus," in 30-second spots three or four times every hour, every night until 11/3. He'll give bombastic press conferences every morning, bragging about all the progress we're making and injections being shipped by the millions. And you can probably guess what he'll be doing on Twitter every night. And if he manages to do all of that before the first or second week of October, he very well could solidify a very comfortable margin of victory.
What I honestly think happened, or is happening now, is Trump got very, very lucky. He's been bragging about all of the "incredible" vaccines that are "coming any day now" for months, promising that they'd be effective and bragging about dumping billions of dollars into the research. And in a monumental stroke of good fortune, it looks like the vaccines being developed are turning out to actually be pretty effective. Who do you give credit to? Well, you can decide for yourself. Historians will likely credit the largest, most coordinated international medical effort in the history of mankind. But that's for later. I promise you that if you give the average American voter a choice between a frail, stuttering, senile old man and his obnoxious bitch running mate who promised you the world would end and you'd all die under Trump, or the devil you've known for four years who's on television every night bragging about the hundreds of millions of doses headed to a pharmacy near you any second now, and there's this cautions but growing national sense of relief and hope that we're just about to reach that light at the end of the tunnel, beat this virus and Trump is promising we're going to get back to "normal" soon (however unrealistic that really is) well...take a wild guess who the average voter goes with.
Historically, Americans don't often switch leaders during conflict or crisis. Pundits and professors sum this up as: "We don't change quarterbacks at halftime." If the Trump campaign can successfully project a theme that we're still at war but winning the war and Trump is about to push us across that finish line and destroy this virus, Trump is getting a second term. And honestly, realistically...I wouldn't want to switch administrations and disrupt operations at every federal agency and department with a national leadership and management overhaul (because this is what happens when you switch administrations) when we're on the very cusp of getting the vaccine and undertaking the largest distribution effort in our country's history. It's just not a good idea, no matter what you think of the sitting President.
But like I said, I'm not interested in the politics of this. I want my vaccination ASAP and that's all that matters to me. If Trump can get that for me soonest, well shit...I'll wear a fucking MAGA hat on my way to the polls to cast my Trump vote.