[Alan Brinkley, the Allan Nevins Professor of History at Columbia University, is the author of “The Publisher: Henry Luce and His American Century,” a forthcoming biography.]

The Times/CBS News Poll shows that there is broad unhappiness with the state of the economy and the performance of Congress, but on the whole the participants seem to be responding fairly normally to a weak economy with high joblessness. The 18 percent of those polled who identified themselves as Tea Party activists, however, have sharply different views — and a sharply different profile — from the population as whole.

The most important clue to the views of the Tea Partiers is who they are: mostly white males, over 45, more wealthy and more conservative than the norm.

This is a profile that matches other highly motivated protests over many decades — the supporters of Joseph McCarthy, for example, in the 1950s. Today, the target is not communism, which is no longer a major issue for the right (although “socialism” appears to have taken its place). But what seems to motivate them the most is a fear of a reduction in their own status — economically and socially....

The real issue, I believe, is a sense among white males that they are somehow being displaced, that the country is no longer “theirs,” that minorities and immigrants are becoming more and more powerful within society. And, of course, they are right about that. They just fear it more than many other Americans.