Michael Gerson in the Washington Post, (and the fact that he's in the Post tells you all you need to know about him as a "Republican")

A second question of Tea Party candidates: Do you believe that American identity is undermined by immigration? An internal debate has broken out on this issue among Tea Party favorites. Tom Tancredo, running for Colorado governor, raises the prospect of bombing Mecca, urges the president to return to his Kenyan "homeland" and calls Miami a "Third World country" — managing to offend people on four continents. [Links in original]

Dick Armey of FreedomWorks appropriately criticizes Tancredo's "harsh and uncharitable and mean-spirited attitude on the immigration issue." But the extremes of the movement, during recent debates on birthright citizenship and the Manhattan mosque, seem intent on depicting Hispanics and Muslims as a fifth column.

There is no method more likely to create ethnic resentment and separatism than unfair suspicion. The nativist impulse is the enemy of assimilation. In a nation where minorities now comprise two-fifths of children under 18, Republicans should also understand that tolerating nativism would bring slow political asphyxiation. [Links added.]

Why the Tea Party is toxic for the GOP, By Michael Gerson, August 25, 2010