AP

AMHERST, N.H. (AP) -- Republican presidential contender Rick Perry is working to convince voters he's tough on immigration.

And he has a key new supporter to help make that case.

Arizona Sheriff Joe Arpaio formally endorsed Perry in New Hampshire Tuesday morning, the first stop in the Texas governor's latest visit to the first-in-the-nation primary state.

Arpaio says he doesn't know Perry well, but likes his border experience. Several candidates, including Mitt Romney, had sought Arpaio's backing.

But at least one prominent Granite State Republican says Arpaio is an embarrassment.

Former GOP chairman Fergus Cullen likens Arpaio to those who used police dogs and fire hoses on protesters during the civil rights era.

Perry has struggled to clarify a Texas law permitting in-state tuition for illegal immigrants.