By Jeremy W. Peters

WASHINGTON — New Hampshire has one of the smallest populations of illegal immigrants in the country. Only about 5 percent of its 1.3 million residents are foreign-born, and 3 percent are Hispanic.

But tune into the Senate race between Scott P. Brown, the Republican, and Jeanne Shaheen, the Democratic incumbent, and you might think the state shares a border with Mexico, not Canada.

When someone called a talk radio show to ask Mr. Brown about global warming the other day, Mr. Brown immediately started talking about border security. “Let me tell you what I believe is a clear and present danger right now,” he said, brushing aside the caller’s concerns about the environment. “I believe that our border is porous.”

Footage of agents patrolling the rocky, arid Southwestern landscape is featured in Mr. Brown’s ads — not quite the piney highlands of New Hampshire. Read more from the New York Times.