The current strat I use is to immediately get to three in California and Texas (maybe Illinois or Pennsylvania in between). Then if the computer has Florida, New York, Illinois, Pennsylvania, Ohio, Michigan, Georgia, North Carolina, or New Jersey (states you'll need by the end to barely reach 270) immediately lock those states down from the computer. If you lose one of those states, I recommend Virginia and Washington as a backup.

So starting off with the California and Texas strats, in my run I got one in California, next turn immediately end turn and in the third turn two more in California for a total of three. Right after California I went after Texas with two campaigns in the same turn, after that immediate end turn and one more for three. It is important to get three at every state so that 1. It counts towards the state groups and 2. The opponent can't tie or take the state in one turn. Having said that it is possible to win without completing three at every state but I haven't personally tried it (possible timesave?). After that you get the same 9 states that Otterstone gamer suggested (Illinois, Michigan, Ohio, Pennsylvania, New Jersey, New York, North Carolina, Georgia and Florida) getting you exactly to two seventy. To trigger the election (or the ballot next turn event) two things must be true. 1. A candidate is leading in every state and 2. A hundred electors worth of states are locked down. To lock down exactly 100 electors campaign to the max in Illinois, Pennsylvania, North Carolina, Georgia and Florida.