Ross Perot had a shot in 1992 but blew it by promoting conspiracy theories (that may have even been true, who knows) about Republican infiltration at (iirc) his daughters wedding.
And the split in the vote let Bill Clinton beat the incumbent Bush.
The only way a third party takes a seat is when they capture the attention.
Locally, that's easier. Less people to win over, you get to focus on local accomplishments, etc. But national you need to become the national conversation or too many voters wouldn't know who you are.
Maybe so. But he's a good example of someone getting 'close' nationally.