The actual harm reduction candidate was... Nobody. There wasn't one. The harm was always going to happen, there was no choice to have less of it. The only choice was who you wanted to do the harm, who you wanted the harm to be done to, and where you wanted that harm to be done.
I don't like to just blame Reagan for everything as it ignores the fact society was already fucked up enough to create and elect Reagan before Reagan was president
Trump is the harm reduction candidate insofar as he galvanizes the libs in Congress to oppose shit like this. The same thing happened with NAFTA. Bush Sr. wanted to do it when he was president and the Dems told him to pound sand. Clinton gets into office and all of a sudden, the opposition vanishes and NAFTA gets through along with welfare cuts and the crime bill.