I fully understand everyone’s assertions regarding incumbents with a good economy. However, I don’t believe the number of people that will vote for Trump this election will increase considerably from the last election. I DO believe that the votes against Trump (not to be confused with support for the opponent) will grow significantly. As I said, I will readily admit fault if Trump wins.
Outcome bias leads people to believe Trump is a stronger candidate than he actually is. Because he trailed in the national polls before the election (yet won the electoral college) a number of people can't help but think a strong economy means Trump has re-election in the bag.
I submit that Trump is a historically weak incumbent - even weaker than George HW Bush - and a strong economy is the ONLY thing making the upcoming race even slightly competitive. We have over 500 days until the 2020 election. The chances of the economy not showing signs of weakness by then are quite low considering recent economic indicators. Obviously the eventual Democratic nominee matters, but there's a significant number of them that can definitely beat Trump.
I bolded the statement above because some people are ignoring the 2018 mid-term elections, and the additional 4 years of demographic changes that have occurred. As we saw in the Alabama special election for Senate, black voters do NOT require an Obama to turn out at a level above their historical norm, if they believe a candidate running imperils their values and beliefs. Furthermore, Hispanic turnout has continued to rise, and Trump has left ample evidence of the impacts of his immigration policy throughout toss-up states like Florida and Arizona, and some might even say, Texas.
None of this bodes well for Trump. His margin of victory in 2020 was razor thin. He won Michigan by 10k votes. He won Pennsylvania by 44k. He won Wisconsin by 23k or so I believe. He won Florida by 1.2%. The Democratic nominee only has to win 3 of those and it's over for Trump -- or just two states if Trump can't hold on to Florida.
Trump's approval ratings and the performance of his party in the mid-term elections show that Trump has NOT expanded his base. At all. His entire strategy revolves around turning out the same voters that previously elected him. But minorities are clearly going to have higher turnout in 2020 than in 2016, and Hillary Clinton was a uniquely unpopular nominee inside of her own party. A number of Democratic voters stayed at home or voted 3rd party because they never dreamed she would lose to Trump, and they wanted to signal their discontentment. That's not going to happen this election.
Compounding all of this is that any hiccup in the economy will sharply undermine Trump's one true strength.
I'll end by saying that few people believed that Doug Jones could win Alabama -- but I did. Back in August before the special election, I said it was very possible and quite doable, and I have the tweets to prove it. I believe that Jones' election is a rough proxy for what happens when you have a controversial nominee run head-first into a buzz saw of increased turnout by minority voters and a drop-off in support for the controversial nominee because people just don't like the idea of that person representing them. Remember, everyone tries to claim the polls got it wrong in 2016 (they actually performed above-average) but everyone always ignores that few polls indicated that Doug Jones had any chance at all.
The question people should be asking is how can Trump beat someone like Biden in Pennsylvania, Michigan, Wisconsin, and Florida. Because I just don't see it. Trump's best chance is for someone like Sanders or Warren to get the nomination, IMO. Even though some of the other Dem candidates actually are polling below Warren, Sanders, and Biden in match-ups versus Trump, there's little predictive value in such polls 500+ days out. That said, I think most of the top Democratic contenders can beat Trump unless he performs an absolute miracle.
Matt will be here very soon to say I got it wrong in 2016. I said repeatedly back then that Trump *could* win but that I thought he'd perform the worst against Hillary out of the other potential GOP nominees. As it got closer to the election, I thought that Trump was unlikely to win. But I also didn't know Russia was running a massive Pro-Trump influence campaign nor did I know how spineless GOP hacks like Rubio and Cruz are. Last, but not least, I also didn't know that numerous Evangelicals held absolutely hypocritical beliefs.
Now I know all these things, and even though I expect additional Russian interference, I believe Trump's weaknesses are such that nothing short of a miracle will see him re-elected. He's just not a strong incumbent and he's only running on a tiny number of issues. He has little legislation or accomplishment that he can point to try to convince swing-voters. The only people that believe he's actually accomplished anything are his base. Everyone else sees that the emperor has no clothes, and that's huge even considering that massive leftward shift the Democratic Party has undergone.