Video: What to Watch For in the GOP Debate  LAS VEGAS – The big question at Tuesday night’s Republican presidential debate on CNN doesn’t involve the candidate who, as he is happy to remind you, is leading all of the polls.  By now GOP front-runner Donald Trump’s debate pattern is pretty clear: Parry potshots from back-of-the-pack candidates by noting how desperate they are to share his attention and dodge moderator questions about the lack of detail or workability in what policy proposals he has made.  Mr. Trump’s position seems unlikely to change during the 9 p.m. contest at the Venetian hotel and casino here. The consensus second place candidate, Sen. Ted Cruz of Texas, has furiously backpedaled in public from a private criticism he voiced of Mr. Trump at a New York fundraiser. Sen. Marco Rubio of Florida has shown no interest in discussing Mr. Trump at all, nor has the falling-in-the-polls Ben Carson. Everyone else is far enough back that Mr. Trump will brush them aside.  That doesn’t mean Mr. Trump will be invisible. Back-of-the-pack candidates like Carly Fiorina, John Kasich and Rand Paul each have an incentive to elevate themselves with a Trump skirmish. Each has tried before. Only Mrs. Fiorina won her battle – during the September debate – but her momentum was short-lived.  CNN says Tuesday’s main debate, starting at 8:30 p.m. ET, will be focused on foreign policy, the exact topic on which the first-term senators from Texas and Florida have been circling each other for weeks. Mr. Rubio is slamming Mr. Cruz for votes to end the National Security Agency’s telephone metadata program. On “Meet the Press” Sunday he said “each time he’s had to choose between strong national defense and some of the isolationist tendencies in American politics, he seems to side with the isolationist.” Mr. Cruz last week tied Mr. Rubio to Democrats calling for gun control after the San Bernardino attack by saying the Floridian wants Americans to “abandon our civil liberties.” This is a real, substantive policy difference that CNN moderator Wolf Blitzer is sure to flush out.  The New Jersey governor is back on the main stage after a sojourn to the undercard session for the Fox Business/Wall Street Journal debate in Milwaukee last month. He has maintained a laser focus on New Hampshire, building momentum by conducting intimate town hall events and keeping himself out of distracting Trump-related news cycles. The question for tonight is how Mr. Christie keeps talking to New Hampshire voters when positioned on a national stage. He also has little to gain with a confrontation with Mr. Trump.  With the energy and discussion around Messrs. Cruz and Rubio and the approaching Trump hurricane – Trumpicane? — the former Florida governor has become almost an afterthought. Mr. Bush has by all accounts a strong Nevada organization, but like elsewhere in the country that hasn’t translated into noticeable popular support. Mr. Bush is so irrelevant that Dan Pfieffer, the former Barack Obama aide who is now a CNN commentator, wrote on Twitter that he has less at stake than any candidate except Mr. Trump.  Mr. Carson meanwhile tried to interject himself into the policy debate Tuesday morning by calling for a war declaration against Islamic State, and proposed positioning National Guard troops along the Canadian border. Recent Republican presidential primary history shows that no candidate who has fallen from the top tier has been able to regain their position.  Messrs. Bush and Carson have a difficult path ahead of them.  When the undercard debate airs at 6 p.m. ET with Lindsey Graham, Mike Huckabee, George Pataki and Rick Santorum, viewers everywhere will ask themselves: Why are these people on my television?  None of the four have generated more than a couple percentage points of popular support. None have paid staff in Nevada, the fourth nominating state on the presidential calendar. None have had a memorable debate moment to propel their candidacies. Republican National Committee spokesman Sean Spicer said on CNN Monday that the party will keep holding second-tier debates as long as there are qualified candidates in the race to compete in them. The question for the networks holding January debates is, Are the lower-tier candidates worth the effort of holding a second debate?  WSJ Poll Finds National Security Now Main Concern  ______________________________________________________ 2016 Election Calendar | WSJ/NBC Polls | 2016 Poll Standings Politics Alerts: Get email alerts on breaking news and big scoops. Capital Journal Daybreak Newsletter: Sign up to get the latest on politics, policy and defense delivered to your inbox every morning. For the latest Washington news, follow @wsjpolitics For outside analysis, follow @wsjthinktank
Washington Wire's Reid J. Epstein previews the inevitable Cruz-Rubio collision, the beginning of the end for Ben Carson and Jeb Bush, Chris Christie's focus on New Hampshire, and more at Tuesday night's GOP presidential debate.