Depends on the Candidate in 2020 for the Democratic Party...
Also it will depend if someone like Sanders runs Green or Third party causing the Democrats to lose votes allowing a weaker candidate like Trump to win.
It would be the Ross Perot effect that happen when Clinton won twice while Perot took votes from the right.
So can Trump win?
Yes.
That is Trumps only path to victory in 2020. Sanders is too smart and principled to run a third party campaign that would get Trump re-elected. I think its unlikely that there will be a viable third party candidate that will split the Democratic vote in 2020. But it is the only way Trump can be re-elected in 2020. The only reason Hillary lost in 2020 is because she left the back door open in Wisconsin, Michigan, and Pennsylvania by not visiting and spending enough money in those states allowing Trump to eek out tiny victories in those states.
Please explain to me and the TV viewing audience at home how money gets you elected? Hillary outspent Trump and STILL lost! What makes you think spending more money makes any difference. Unless you are buying votes, which she probably was doing under the table, what good is it? Her ads sucked, her appearances were lackluster, and she nearly killed herself trying to keep up the pace with Trump! How would money have changed that?
Its marketing 101. When you want to increase sales, advertise more. More money spent in a particular state, means more adds and more people on the ground going door to door to remind registered democrats to get to the polls. All of Trumps victories in Wisconsin, and Michigan, and Pennsylvania are small enough to be corrected by stronger get out the vote campaigns. The more registered democrats who are contacted to go to the polls, the more they show up and vote for the parties nominee. All campaigns, both Republican and Democrat use the same strategies when getting out the vote. When you spend more money in a state, you increase the amount of contact you have with registered voters of your party in that state.
FACT 1: In Wisconsin, Trump only got 1,405,284 votes in 2016 and won the state.
FACT 2: In Wisconsin, Romney got 1,407,966 votes in 2012 and LOST the state by 7 percentage points
What this shows is that Trump actually did worse than Romney with Republican voters, yet he won the state. Why? Because too many registered Democrats stayed at home and did not vote in the 2016 election. What would have increased Democratic turnout on election night in 2016 in the State of Wisconsin? More money being spent in the state on the get out the vote campaign as well as Hillary Clinton actually visiting the State. Hillary Clinton NEVER visited Wisconsin during the campaign. The result of that would have been Hillary winning the state by a minimum of 50,000 votes instead of losing the state by 22,000 votes!