Charles Frahm, FBI deputy assistant director for counterterrorism, said there is increasing concern that the most radical elements of the anti-immigration wing may be "susceptible" to recruitment by white supremacists and other groups inclined toward violence.
Police departments across the country also are uneasy as political divisions regarding immigration enforcement have raised local tensions.
"This is certainly a concern for every police chief in the country," said Charlotte-Mecklenburg, N.C. Police Chief Darrel Stephens, president of the national Major City Chiefs Association. "As long as the issue remains unsettled, the tension grows."
Perhaps not since the anti-government militia movement came to prominence in the early 1990s, the Southern Poverty Law Center says, have so many groups embraced such a common campaign for dealing with what they describe as failed government policy.
"The infection is spreading," said Mark Potok, editor of the center's Intelligence Report.
"It's no longer unusual to hear vilifying fairy tales of immigrant-borne secret conspiracies and massive criminality on radio, cable television and even in the mouths of pandering politicians," he said.
"A functioning police state needs no police." ---William S. Burroughs
"There is no sense and no sanity in objecting to the desecration of the American flag when we tolerate, encourage, and as a daily business promote the desecration of the Country for which it stands." ---Wendell Berry