A government trifecta = One party controlling the US presidency, senate, and house.

Independents are grouped in with whichever party they caucus with.

In the event of controversy over if a certain government formation constitutes a trifecta, I will resolve based on whatever this wikipedia article says, ignoring things like vandalism (I will use my own judgement to determine when it's appropriate to resolve the market): 

https://en.wikipedia.org/wiki/Divided_government_in_the_United_States

If I am no longer using this site when this market should resolve and there is controversy, resolves based on wikipedia, or if necessary trustworthyish consensus on if the government is a trifecta or not.

In the event the next trifecta is for a party not listed, or the structure of government changes significantly such to render the concept of a "trifecta" no longer applicable, resolves N/A.