The term "doughface," or "Northern men with Southern principles," is used by historians to refer to pre-Civil War politicians from free states who supported slave-state politicians on issues (like territorial laws and fugitive slaves) pertaining to slavery. The word was coined by the outre Virginia Senator John Randolph, who said that pro-slavery Northerners were so afraid of the South that "they were scared at their own dough faces." This may have been a reference to a children's game, but no-one thought to ask Randolph, who was an eccentric crank with a short temper. (Leonard Richards, The Slave Power, [LSU Press, 2000], 85-86)
The Doughface presidents, properly called, were the three Northern politicos who held the White House in the 1850s and actively exerted themselves to appease Southern white radicals. They ostensibly did so to hold the Union together, but their actions contributed to the immiseration of black slaves and were also unpopular among Northern whites. They thus placed a rather tarnished ideal above the lives and interests of a substantial part of the population. (While Lincoln allegedly valued the Union as much as the Doughfaces, his refusal to compromise on the issue of slavery in the territories helped ensure the Union would break up in 1860-61.)
The Three Amigos were
Millard Fillmore (New York, 1850-53): A Whig who succeeded to the presidency upon the death of Zachary Taylor, and who not only signed the infamous Fugitive Slave Act of 1850 (which compelled Northerners to assist slavecatchers) but zealously enforced it. In a particularly infamous episode, Fillmore indicted for treason several men indicted for attacking slave-catchers in southern Pennsylvania. The jury acquitted them. Paul Finkelman's biography, which I briefly reviewed here, has more details on why Fillmore isn't just an obscure nonentity.
Franklin Pierce (New Hampshire, 1853-57): Democrat who sent federal troops to Boston in 1854 to escort runaway slave Anthony Walker back to Virginia. Pierce's action helped turn many moderate Yankees into abolitionists. He also signed the Kansas-Nebraska Act, which permitted the inhabitants of those territories to admit slavery if they chose, and supported the forcible installment of a pro-slavery government in Kansas.
But the Palme d'Or for ultimate presidential asshattery goes to
James Buchanan (Pennsylvania, 1857-61): Endorsed the ghastly Dred Scott versus Sanford decision. More or less destroyed his own party (the Democrats) by bribing Northern Congressmen to vote for the Lecompton Constitution, a blatantly fraudulent and authoritarian pro-slavery constitution for the future state of Kansas, and by attacking Democrats like Stephen Douglas who refused to go along with it. Supported re-opening the African slave trade, half a century after the U.S. and many European states had outlawed it as an insupportable evil. And, while we can't blame every U.S. president for the actions of their Cabinet secretaries, we may note that Buchanan's secretary of war was a Southerner who tried to send artillery to the Confederacy shortly before the end of JB's presidency. Really set the gold standard for presidential awfulness.
Buchanan's two predecessors had equally discreditable post-presidencies. Fillmore ran for the presidency again in 1856 as the candidate of the xenophobic Know-Nothing Party. Pierce openly sympathized with the Confederacy and ran over an old woman with his carriage. Buchanan, at least, had the good grace to do nothing in particular until he dropped dead in 1868.
Professor Osburn suggests we establish an Anti-Presidents' Day for the worst U.S. presidents, which would be most of them. We differ on the best date for such a commemoration; my preference would be for January 9th, Richard M. Nixon's birthday, but your mileage may vary.