ednesday night's Republican presidential debate is on CNBC, whose business-minded moderators have asked questions to Donald Trump, Ben Carson, and Ted Cruz challenging the wisdom of their approaches to the federal budget. Trump and Carson have proposed massive tax cuts that nonpartisan and even conservative analysts have said would raise the deficit by trillions of dollars. Cruz has famously pushed the U.S. to the brink of defaulting on its debt, which almost everyone—including the leaders of his own Republican Party—agrees would be a catastrophe. CNBC also asked Marco Rubio a pointed question about his frequent, well-documented absences from the Senate,...