problem is, you only have right-ish non-3rd parties. In Portugal the 2 most voted or the big ones are very close in the center, one is center left, another is center right, and since the revolution we've been with one or another. Good thing the ones your call 3rd parties are also very important,
Nationalist Party (not dumb but surely do foolish stuff)
CDS-PP (Right democrats) (probably the strongest right wing third party, normally connected with PSD (Social-Democrats), a center-right party)
PSD (social-democrats, big one, although the guy leading them is a stupid ass)
PS (Socialist, the ones in power, another big one, and yes I'm happy)
BE (Left-Block, very important third party, emerged from nowhere and it's the best and biggest opposition tot he government, it's the most professional one in my opinion, actually gets very appealing propositions to the government)
PCP (communists, also very important third party, close to BE but yell about workers and unemployment.)