C. 26
Absolute bare minimum? Eleven. California, Texas, New York, Florida, Pennsylvania, Illinois, Ohio, Michigan, Georgia, North Carolina, and New Jersey total exactly 270 electoral votes, which is the bare minimum needed to win.
It’s a practically meaningless question, though, since there is about a 0% chance of a candidate being able to carry those eleven and no others. Texas, Florida, North Carolina, and Georgia have been heavily Republican for about as long as California, New York, Illinois, and New Jersey have been heavily Democrat. So if those states are all going for the same candidate, they’re bringing a lot of other states along with them. But yes, based solely on the number of electoral votes, it could be done with just eleven of the 50 states (and DC