David Broder has breaking news in the presidential race. He has discovered, through his own investigation that — brace yourselves — none of the leading Democratic candidates for President has executive experience. He points out that this leaves the Democrats at a serious disadvantage to their Republican counterparts: It was fascinating to watch the three top contenders for the Democratic nomination discuss their concept of the presidency during Tuesday night’s MSNBC debate in Las Vegas. But it was also stunning to realize that the three current and former senators who have survived the shakeout process — Hillary Clinton, Barack Obama...