Good morning. It's Texas, Ohio, Vermont, and Rhode Island primary day.

Today could be the mother of all primaries; the primary to end primaries; the primary royale--so make sure you're up to speed.

Read our in-depth primers on the Texas and Ohio contests; check out Jonathan Cohn's up-close look at Hillary's last minute pitch to the voters in Toledo, Ohio; game out every possible scenario with Noam Scheiber, and keep your eye on tonight's bottom line with Jonathan Chait.

--Barron YoungSmith