The problem is that Mississippi has long operated as a state that functionally had an open primary.
The opposition Socialist Party's open primary on Sunday drew a surprisingly high 2.5 million voters.
Paul has consistently done best among young voters and independent voters in open primary states.
Texas has an open primary, and in another break for him, this year it made its primary fully proportional.
Arkansas has an open primary on May 22 and a deadline of Feb. 10.
He beat five Socialists, including Royal, in an open primary last October.