If only I had mod points...
The closest any third party has come to a presidential election was Ross Perot, in 1993. He had a very well-oiled hype machine and a shitload of money, which is why he got as far as he did. Even after he began stumbling and his campaign imploded (hard), he still got 13% of the vote... pretty impressive by most standards of the modern era.
On lower levels, Bernie Sanders (nominally a member of the Socialist party, but caucuses with the Democrats 99% of the time) is the only national candidate period to have made a national office since what, the 1950's?
It's going to take a radical change in attitudes, a really rotten national situation overall, and an even more radical amount of disgust with the current system before folks wander off to vote for a third party. Even when some ideological icon does run on his own (e.g. Ralph Nader), you will see the immediate (and dishearteningly effective) rallying cry of the threatened major party (in Nader's case, the Democrat party immediately started screaming "OMG you'll split the vote and then they will win!")
It'll take a lot to get a third party off the ground. Not impossible, but it'll take a lot to happen nonetheless.