We have not yet seen a candidate running on a socialist proposal coupled with even mediocre or passable mediatic support. Every time a socialist-leaning candidate pops up, moneyed interests work really, really hard against them. However, it's getting better and better (see: Corbyn in UK).
It'll come. People will vote themselves, not bread and circuses, but health and education. And democracy and markets, as opposing decision-making mechanisms, will clash.
Or just populism in general - and I think "fear" is a stronger voter-pull than "want": fear of Mexican immigrants committing crimes, taking your job, fear of increased healthcare costs, etc.
As the majority of Americans do have health coverage it's a given that 51% of the population want cheaper coverage even if it means the other 49% will lose coverage then that's going to happen.
(Which is why politicians are so busy denying that anyone will lose coverage under their plans.)
If you mean a third party, well than that comes down to lack of trust in that party's ability to execute.
This party is still not in power. I don't think its a foregone conclusion that people vote themselves bread and circuses, which is I think your primary point.
On another front I find it hard to believe that UBI if it ever comes to the US will be set anywhere above poverty level. In that context anyone who voted to take money from people in poverty and use it to build roads they would probably be laughed out of office and rightly so.