Answer: Democrats!
I'll be very interested to see, when the dust settles tonight, if the polls are more on the money in states with closed primaries, where bored (or wily) Democrats can't vote in the Republican Party primary for Haley. A lot of the exit polling data we've seen on Haley supporters and who they'll vote for in the general election, or whether they approve of Biden's job performance, makes me wonder how many of her voters are just plain old Democrats who are getting screened out of a lot of GOP primary polling. But we'd see a difference in closed primary states (to the extent we have robust polling there to make the comparison)!
—Jacob Rubashkin, Inside Elections