http://freakonomics.com/podcast/politics-industry/
Unfortunately to change the law you need voters who vote for a party that is willing to change it even though it came into power under the current law.
It's something to think about if you don't like the candidates the major parties are running and thus assume your vote means nothing.
Search for "Minor party candidates" here for the specifics: https://www.fec.gov/introduction-campaign-finance/understand...
https://mises.org/wire/26-percent-eligible-voters-voted-trum...
If you do not vote or vote for someone you do not want, your vote is worse than lost.
There is much potential for other parties. And while the presidential election is most important regarding war and the rest of the world, other elections for local politicians are important too and maybe even more important for US citizens.
Related talk: How To Eliminate The "Spoiler" Vote Phenomenon w/Jill Stein pt. 1 https://www.youtube.com/watch?v=bgYEFxjJaUg