It was quite possibly the understatement of the year. Senate Majority Leader Mitch McConnell, in a Bloomberg Politics podcast last week, said Donald Trump "doesn't know a lot about the issues."

Trump isn't a blank slate, exactly. He wants to ban Muslims from entering the United States, deport 11 million undocumented immigrants and build a wall to keep Mexicans out. He wants less open trade. And while he opposes gun control, he'd ban gun sales to anyone on a terrorism watch list.

But Trump's thinking on a host of other issues — the details on taxes, federal budgets, deficits and debt, income inequality, the cost of child care, charter versus public schools, housing, student debt and many other things supposedly on voters' minds this year — isn't clear.