Being a protest party in parliament

You know the story: a new political movement appears and quickly surges in the polls. It wants to upend the political system. It says that older parties failed voters and ran the country into the ground. They organise huge protests and claim that politics is happening on the streets, not in the national assembly.

Two scenarios can follow. The first is the more common: the movement fails to establish itself as a functioning organisation, and quickly falls apart, often assisted by infighting among rival leaders. The second scenario is more interesting: the movement transforms into a real party with a clear leader and platform, does well in the next election and enters parliament.