It seems likely that if you have a voter who believes all three of:
1. The current economy is great, much better than it was under Obama.
2. This is primarily because of things that Trump has done while president.
3. The economy is a primary factor determining who they will vote for.
Then it will be extremely difficult for any democratic candidate to get their vote.
I think the right response is to hope that the voter in question is not wholly convinced of at least one of the three propositions. So the right response is to:
1. Point out that current economic growth is not really any better than it was under Obama. Point out that a lot of people are struggling with costs for education, health care, and housing, and that the current economy hasn't been great for everyone. Point out that while there are a lot of jobs (low unemployment), many of these are the "gig" sort of jobs or jobs that pay a minimum wage that hasn't gone up in a long time.
2. Point out that a lot of things that Trump promised about the economy haven't come true. The big Republican tax cuts didn't really lead to wage growth and instead were invested into stock buybacks. Farmers are struggling because of Trump's trade wars. The coal and steel industries Trump promised to revive aren't doing well and have been closing plants he promised would stay open.
3. Bring things back to the staggering corruption (huge amount of self-dealing by Trump's family and appointees) and cruelty of this administration (children in cages, supporting murderous dictators world-wide, deporting long-time members of communities with no criminal records, etc).
Again, there are certainly some voters who will say "I am making more money than I did four years ago so Trump is great" and just ignore all the racism and cruelty and corruption, all the broken promises, etc. And we can argue about whether such voters are racist themselves (because they are willing to overlook racism for a few extra dollars in their bank account) or whether they're just oblivious. But I don't think they are reachable voters in most cases.
If you look at Trump's approval ratings through his presidency, you will see that
they are extremely stable. He has been pretty much at 42% approve and 52% disapprove for a long time. You might think these numbers would go up and down depending on the news (economic or otherwise) but they really don't. That suggests this will be more of a "turnout" election than a "convince the voters" election -- there are very few voters likely to change their minds at this point. Fortunately for Democrats, Trump is consistently unpopular. The risk is that he might be able to win the electoral college anyway (he was unpopular going into 2016 too and he did lose the popular vote), and Republicans have ramped up the voter suppression efforts in recent years. It will likely come down to ground game, but I think a high-turnout election is likely because Trump is so polarizing (see 2018) and this will probably work to Democrats' advantage.
Adam W. Meyerson
a.k.a. Appeal Without Merit