Two party system is basically a form of government whereby only two parties are officially recognised. There's the ruling and opposition party, the opposition party is officially recognised unlike in multi party system. When I mean two party system I don't mean PDP and APC. I mean political parties strictly based on ideology which the two parties I mentioned lack that's why there's usually a Cross-carpeting. Let's take America as a case study. Blue and red which is Democratic and Republican Party respectively. These parties are based strictly on ideologies and their members rather retire than cross carpet.

Hmm