Here in the US, we don't have democracy now. We have a two party, democratic REPUBLIC. The politicians can pretty much do whatever they want after they have been elected because the media has conditioned us to believe that we have only two parties from which to choose (i.e. - "bipartisan").
The two party system in the states has its beginnings in the divide between mercantile Hamilton and the agrarian Jefferson in Washington's first Administration.
"Party discipline" doesn't exist in the states as any European or Canadian would understand it.
The major parties are loosely bound coalitions based on issues, geography, personalities and so on. But a loosely bound coalition can be remarkably enduring and effective.
The third party in the states forms around a single issue or set of issues and a lone charismatic leader - when one or the other are extinguished, the party dies as well.
In American culture, three is the unlucky number. The also-ran.