Tonight is "Western Tuesday," featuring primary elections in Arizona and Utah. Current polls on the GOP side suggest Donald Trump will win Arizona while Ted Cruz will win Utah.
Political commentators noticed something interesting early on about Donald Trump's surprising sweep through the Republican primaries — the mogul seems to do better in states that let almost any voter help pick the party nominee, not just those registered to a party.
In those open primaries, Trump has come out ahead in 13 out of 16 states. In states with closed primaries, Trump won only six out of 14 states. Overall, Trump has won closed states about half as often as he's won those open states.
Both primaries in Utah and Arizona are "closed," meaning only registered Republicans can vote. They're representative of what is ahead in the next few weeks: Of the 19 remaining primaries, 13 of them will be closed. That could be bad news for Trump if he wants to cruise to the convention uncontested.