Cook Partisan Voting Index
Cook Partisan Voting Index is the unit used to calculate how much a particular place leans towards each party.
Two states, Pennsylvania and Wisconsin, are completely nonpartisan. The other 48 states lean either towards the Republicans or Democrats. The most Republican state, according to the CPVI, is Wyoming, which is R+25 on the CPVI scale (meaning that the Republicans have a 25% lead over the Democrats there). In contrast, the most Democratic state, Hawaii, is D+18, meaning that the Democrats have an 18% lead over the Republicans there.