The rules differ by state, but it's possible! How can we get this info to the Trump campaign so they can get the message out to voters who have changed their mind?

Michigan: Voters need to submit written requests to their city or town clerks

Wisconsin: Same, but deadline appears to be October 29

New Hampshire: You can show up within the first hour of November 3rd voting and may be able to change your vote

Pennsylvania also seems possible, but the rules are a bit murky.