Scott Walker is a tough-as-nails governor. He has an appealing demeanor and a record of fighting the liberal machine in Wisconsin. The base is increasingly rallying to him, as evidenced by his second-place finish in the CPAC straw poll, well ahead of hard-line conservative favorites Dr. Ben Carson and Sen. Ted Cruz (R-Tex.) But he has a real issue that cannot be ignored: There is a serious question about how much he knows beyond state issues and, hence, whether he is prepared for the presidency.

Wisconsin Gov. Scott Walker (R). (Andrew Harrer/Bloomberg)

In London, he swatted away an evolution question, which was, I think, smart given how irrelevant it is to any real issue he will encounter. But he refused to answer any foreign policy queries. At CPAC, he gave a forceful speech, but when asked how he would fight the Islamic State he gave a non-answer. He then suggested he was ready to be commander in chief after dealing with 100,000 union protesters. It was inaptly put, but the absence of substantive answers and the comparison to a handful of candidates who spoke in-depth on an array of national security issues left some supporters shaken.

Then came his appearance at Club for Growth. The coverage has been harsh.

The Wall Street Journal reported, “The event was moderated by Frayda Levin, a member of the Club board who is supporting Kentucky Sen. Rand Paul in the coming presidential race. In addition to her direct questioning on foreign-policy, Ms. Levin grilled Mr. Walker on what changes he would make to the Dodd-Frank financial-markets reforms. After a lengthy answer in which the Wisconsin governor failed to suggest specific changes, she referred to concerns small community banks have with the law and asked him, ‘So, are you just not that aware of what’s happening with Dodd-Frank?’ ”

Asked about foreign policy, he said the most important foreign policy decision in his lifetime was Ronald Reagan’s firing of the air traffic controllers. It is a defensible answer as regards to the Reagan presidency since that set the tone for the Reagan Cold War positioning, but, of course, in Walker’s lifetime there have been the Gulf wars, the Iraq surge, the response to 9/11, the reunification of Germany and a host of other events. An adviser with a rival campaign conceded that former secretary of state George P. Shultz, who has met with many presidential candidates, often observes that was a critical moment in the Reagan presidency, but the adviser argued that it was “not in any way a foreign policy decision and therefore no one would ever call this the most significant foreign policy decision in anyone’s lifetime.” The adviser added,”To call it a foreign policy decision is completely ludicrous.”

Moreover, Walker seems stuck on one talking point, toughness against unions, which underscores his lack of foreign policy experience. The moderator at Club for Growth went so far as to tell Walker the word from New York donors was that he was “not prepared to talk about foreign policy.” Walker fed the narrative that he is solely concerned with economic issues by dismissing as distractions other questions he has been asked lately.

He did not help himself today when asked about ground troops to fight the Islamic state. “For me to do something like that would require a number of things: Listening to the chain of command, particularly the Joint Chiefs and national security advisers and others, as to what’s necessary, and listening to the people who are actually out in the field is the best way to do that.” But military leaders will disagree, and he wants to be commander in chief. There has to be more to his answers than this.

This might not be an immediate problem, had Walker not zoomed to the top of the polls. But these events, if not erased by evidence of real knowledge of the issues and foreign policy sophistication, will hurt him. This is a contest with many good candidates who will try to show their superior knowledge and experience; voters have many choices this time around.

This is the nature, however disturbing, of presidential campaigns these days. A few incidents create a “pattern” that turn into a “narrative” that become a problem. Walker, especially because he does not have a college degree, cannot afford to be put in a box labeled by the MSM: “Another Know Nothing Republican.” Richard Grenell, a former spokesman for the United States at the United Nations and briefly with the Mitt Romney 2012 campaign, put it fairly: “GOP presidential candidates must recognize what they don’t know and educate themselves quickly — especially on foreign policy. We must have a candidate that is tested and a team that is aggressive.”

Walker cannot win if he becomes merely the favorite of the conservative base; he has to show the entire party and the country at large that he is ready to stand on the stage with Hillary Clinton and, if elected, take on the job of commander in chief. Former U.S. ambassador to the United Nations John Bolton put it this way: “Protecting the country is the President’s primary responsibility. As I said in my CPAC speech, the eventual Republican nominee will have to be ‘ready for Hillary’ on national security.” He added: “That means more than giving an occasional speech or focus-group tested talking points.”

Following President Obama — who lacked experience and allowed the world’s problems to spread and deepen — the 2016 GOP hopefuls may have a higher bar on foreign policy to jump over than any candidates in recent memory. That means Walker must get cracking, and fast before the media and his opponents, however unfairly, define him in unflattering ways.