Trump won the dark purple states (WI, MI and PA) in 2016 by less than 1% of the total votes. The light purple states (FL, OH and IA) also went for Trump in 2016 but voted for Obama in 2012.
The light red states (AZ, TX, NC and GA) are ones that could still swing Democratic in 2020. The light blue states (ME, NH, VA, CO, NV and NM) are the ones most vulnerable to turning Republican. There was less than 10% difference in the 2016 voting for the two candidates in these states.
The 2016 winner in solid red states (UT, MO, LS, MS, SC, AK and IN) and solid blue states (CT, RI, NJ, DE, MD, WA, HI, IL and OR) got at least 10% more votes than their opponent, making it very likely that those states will remain respectively Republican and Democrat in 2020.
In the dark red states (ID, MT, WY, ND, SD, NE, KS, OK, AR, AL, TN, KY and WV) and dark blue states (CA, MA, VT, NY, MD and DC) the 2016 winner got at least 20% more votes than their opponent, making it almost impossible for the opposing party to win in those states in 2020.
Hover over the state to see the number of electoral college votes it has. Click on the state for more details.