This is how third parties currently work in the US.
They could easily get big enough to take house and senate seats. But the reason they don’t is because of structural impediments (
@aguerrrroooooooooooo and I were discussing a bit further up the thread) that prevent them from taking the seat where the real money and power is: the presidency. When you can compete for the pinnacle of political power in the US is very difficult to gain supporters, funding, and influence.
Until that is rectified they will always be merely “influencers” and “pushers”, inevitably being consumed by one of the Republican or Democratic parties once they have adopted enough of the third party platform to satisfy the members of that third party. Then the cycle repeats.