Persuading people to vote 3rd party is just one piece of the puzzle. Some will vote 3rd, others stay home and some morons can be convinced to vote for the pedophile party. It adds up. 3rd parties are also convenient in sewing doubt in the D candidate. If you show people there’s an obscure party that will offer world peace and free healthcare, D voters will be disappointed in their candidate, but the R voters don’t even hear the message. The US election system is complete garbage, but you have to play with the D or R rules.