If you mean to combine opposition to ethnic minorities into a single category identified more with one party or another, that's impossible to do for most of American political history because the parties interests diverged depending on the particular race and social characteristics of the minorities in question.
In the second party system, Whigs were (among other things) the party of middle class Protestant social and moral reform. This meant they were on the whole relatively more humane than the Democrats when it came to blacks and indians, but also led to opposition to what they saw an invasion of illiterate Catholics who would threaten the character of the nation. Outside the South, these Whigs mostly joined the Republicans eventually, along with free soil Democrats, and some new immigrant communities (ex St Louis Germans).
Still among the Democrats you could find plenty anti-immigrant sentiment also, leading to intraparty battles, in some elections splitting the party in two. (iirc there was an antebellum mayoral election in New York City fought mainly between two Democratic factions over nativism.) The 1860 split between the Democrats was mostly regional (North v South), but immigration also mattered. Immigrant communities tended to support Douglas, even in the South where most Democrats supported Breckenridge. In Connecticut, Breckenridge had the support of half of Democrats - those who held more conservative, agrarian, and nativist views.
Thanks for helping answer something I asked a few days ago.
I viewed Breckinridge as the candidate of just Southern Democrats exclusively...
