As much as I liked Jill Stein, the Green party is a joke. Every third party in the U.S. is a joke. The only viable option for reform is to infiltrate one of the two existing parties. Your name will not live on, but your policies might.
Indeed, the New Deal, Civil Rights, and same-sex marriage all happened without third parties. Generally, American third-parties = unelectable loons.
Yeah. It's not like we directly elect our Senators instead of having state legislatures appoint them.
Well I'm talking about right now; during the 19th century, and even the first part of the 20th century, this wasn't true. That said, keep in mind that WJB ended up integrating the Populist Party's platform into the Democratic Party, and Teddy Roosevelt made progressivism mainstream in the Republican party (until 1912).