According to this anti-Catholic pamphlet issued in the 1920’s, they did. In the years following the Civil War, every time a wave of anti-Catholicism engulfed the United States (which it frequently did into the 1920’s), some person or group published a leafelt, booklet, even a book, claiming that the Vatican was to blame for the President’s death. Charles Chiniquy, an ex-priest turned rabidly anti-Catholic Protestant minister, claimed that Lincoln told him the Church of Rome was a threat to American liberty. (Scholars doubt whether Chiniquy even met Lincoln.) Much was made of the fact that some of the Lincoln conspirators, including Mary Surrat and her son John, were Catholic. Others claimed that the Jesuits, as the Pope’s shock troops, engineered the assassination. According to their line of reasoning: The Pope hated the notion of democracy, preferring instead theocracy. Lincoln was dedicated to upholding democracy. Therefore, Lincoln had to be killed, and the Pope looked to the Jesuits to carry it out.
I am not a Know-Nothing. That is certain. How could I be? How can any one who abhors the oppression of negroes, be in favor of degrading classes of white people? Our progress in degeneracy appears to me to be pretty rapid. As a nation, we begin by declaring that “all men are created equal.” We now practically read it “all men are created equal, except negroes.” When the Know-Nothings get control, it will read “all men are created equal, except negroes, and foreigners, and catholics.” When it comes to this I should prefer emigrating to some country where they make no pretence of loving liberty-to Russia, for instance, where despotism can be taken pure, and without the base alloy of hypocrisy.