Politics NEVER changes from the top down. You don't elect some absolute newcomer who circumvents all the normal paths and then completely revolutionizes the country. (At least not in a stable, functioning society.) Politics in the US happens from the ground up. Not top down.
If any third party was serious about changing society, they would start at the local level. Then, after proving that they can enact meaningful change and bridge the divide between the huge political span that Americans hold, they would sweep their state elections and federal elections.
All of these pie-in-the-sky parties who think that they will win the presidency and then somehow enact society-changing legislation (_the president doesn't make laws!!!_) are either fools or charlatans.