I'm rereading McPherson's classic with a friend, and I came across this passage in his examination of the relationship between Republicans and the anti-immigrant Know-Nothings:
On the other hand, many antislavery leaders recognized the incongruity of nativism with their own ideology. "I do not perceive," wrote Abraham Lincoln, "how any one professing to be sensitive to the wrongs of the negroes, can join in a league to degrade a class of white men." William H. Seward had battled nativists in his state for more than a decade. . . An "anti-slavery man," said George W. Julian, founder of the Republican Party in Indiana, "is, of necessity, the enemy of [this] organized scheme of bigotry and proscription, which can only be remembered as the crowning and indelible shame of our politics."
Imagine what they would say about their own party today!