Dear sinkspur,
"Other than Ross Perot, who gave us Bill Clinton, name one other time."
In the 1850s, there was one party committed to the preservation of the institution of slavery - the Democrats. The opposing party, the Whigs, was not so committed to it, but neither were the Whigs intent on the eventual goal of freedom.
A small third party ran its first presidential candidate in 1856, and lost. I suppose a lot of folks didn't give that party a chance. However, in 1860, that party managed to win the presidency, and managed to win the presidency every election until 1880.
The Whigs disappeared.
It's happened before.
sitetest
Recent third party history does not give those who want a viable alternative much encouragement. They all want to start at the top, rather than doing the hard grassroots work.