Countdown to Democrat Debate

The Republican presidential debates have become appointment television. Tens of millions of Americans have tuned in to watch Donald Trump whack his unwieldy field of opponents — pooh-poohing Jeb Bush’s energy level, for example, or disparaging Rand Paul’s appearance.

The shadow boxing that Hillary Clinton and Bernie Sanders have played at for months -- they've barely mentioned each other on the campaign trail -- will give way to more direct jabs Tuesday night.