How have minor parties contributed to the US politics?

Causing major parties to consider, and sometimes adopt, their ideas. Often, it takes a smaller party to put forward a new or potentially controversial idea-- it may not be a bad idea, but it may be...

minor parties change election results by pulling votes from major party candidates?

Because the current government system supports major parties more with the franking privilege and funding. Minor parties still run because sometimes they can bring up issues not normally brought up...

Party renewal is the idea that partys are still importants and do play an imprtant part in american politics, even though there are some which believe that the US is suffering from party decline

Minor parties take votes away from the candidates of other parties.