New Jersey Gov. Chris Christie has made national security the focus of his campaign. Underscoring his focus on fighting Islamic terrorism, his super PAC is airing this ad (his 9th in New Hampshire) entitled “Radical,” beginning today in Boston and New Hampshire:

His final line –“If we don’t protect each other, no one will” — sums up the anxiety and urgency many voters now feel. With national security zooming to the top of the list of voters’ concerns, Christie is making a reasonable bet: After the flirtation with Donald Trump and the two freshmen senators, the public will turn to someone they trust to keep them safe. Hence, he now talks as much about his time as a U.S. attorney prosecuting terrorists as he does his tenure as governor.

At the debate tomorrow one can expect, to put it mildly, a vigorous debate as to who’s most capable of not just beating Hillary Clinton but also serving as commander in chief. You can expect something along these lines:

Trump, former Florida governor Jeb Bush, Sen. Marco Rubio (R-Fla.) and Christie will accuse Cruz of pandering to isolationists at the expense of national security, citing Cruz’s votes on curtailing the National Security Agency metadata program and voting against the defense authorization bill. Cruz will try shrugging it off, making the issue about immigration and accusing all but Trump of being lax on border security. As Trump hits Cruz for his poor “temperament,” Bush and others will point out that’s an odd accusation coming from Trump. Rubio and Cruz may point out that Trump has already made himself so toxic as to prevent his trip to Israel from going forward and to offend Arab allies whom we badly need to stick with us in the fight against radical Islamists.

While political elites focus on the details (Who had Syria figured out? Should we add to ground troops in Iraq?), most voters are going to get an overall sense of the candidates’ comfort level with these issues and their sense of command and confidence. The most effective debate question may be to query the candidates on what emergency situations they’ve faced and how they’ve dealt with it. It may be a head-scratcher for candidates whose brief political lives have been untouched by tragedy, crisis or disaster.

It is possible after the first two states, Christie is the only governor or ex-governor left standing. (If Ohio Gov. John Kasich and Bush do poorly in New Hampshire, why continue on?) At that point, Christie’s argument, which his latest ad begins to make, will become more pointed: Who ya gonna trust to keep you safe — the freshmen kids, the bombastic real estate mogul or me? First, however, he’ll need to traverse this and the January debates as well as best some of the leaders in New Hampshire.