He laid out a detailed plan to crush the Islamic State three months before the Paris terrorist attacks. He gave a well-received speech on rebuilding America’s military at the Citadel two weeks ago. He has shown new confidence discussing terrorism, the Syrian refugee crisis and American values, and how they intertwine.

But instead of winning a second look from voters, Mr. Bush continues to be ignored, and to languish in the polls, even as the nation contends with what he calls “serious times that require serious leadership.”…

Mr. Bush has been the beneficiary of $30 million in television ads in the early voting states, more than any other candidate. One commercial, “Leader,” featured footage from his speech at the Citadel military college in South Carolina calling for a United States-led coalition to destroy the Islamic State “with overwhelming force.”

But the ads have not budged Mr. Bush’s low standing in polls. Of Republicans who named terrorism and foreign policy as their top concerns in a Quinnipiac University survey of Iowa last week, only 4 percent picked Mr. Bush as their top candidate. A national survey by the same pollster on Wednesday gave Mr. Bush 5 percent over all.