Radical? Maybe. Impossible? Definitely not. Emancipation bills had passed in Northern states within living memory all the way up to 1860, with the most recent being in 1848. Those were instant emancipations, without compensation, along the lines that later happened with the Thirteenth Amendment. However, they were also laws that essentially freed a small number of very elderly enslaved people who were born too soon to fall under decades-prior gradual emancipation laws that freed enslaved people when they reached a certain age, provided they were born after a certain date.

The abolition of slavery in the American South was a different story and one on which white Northerners had developed a variety of views. A small minority believed that immediate, uncompensated emancipation was just and therefore should be done, whatever the consequences to the white South's bottom line. Most whites viewed that as a kind of especially dangerous anarchism which should possibly be met, at least on occasion, with a violent response. Far more considered it just so wildly impractical as to be impossible. There were too many enslaved people and too many enslavers. The conservative-to-mainstream white antislavery stance in the North from about 1830 onwards is that emancipation must come, someday, but it must come gradually and with compensation to the enslavers for their lost property. It would surely be the work of decades and probably needed to take the form of removing black Americans entirely from the sight of white Americans. Just where they would be exiled to varied, with Liberia being the most common place but also some discussion of the Caribbean or a part of the American West uncolonized by whites. It was widely understood that this would take the work of at least a century and had to happen with the full and enthusiastic cooperation of white enslavers.

The latter is a tremendous catch, of course. By around the War of 1812, a sort of perceived bargain existed between the white North and white South. This was not an explicit deal, but a kind of modus vivendi that the white North thought had been worked out. The Yankees would not do anything to disrupt or undermine enslaving where it already existed in the South. In exchange the white South agreed that enslaving people was in principle bad and they were going to do something about it, eventually. This involved a whole lot of the white North taking the enslavers' at their word when they made vague complaints about how enslaving people was unjust and a staggering amount of willful ignorance in all those times when enslavers were caught off guard or just didn't care and said what they actually thought: that enslaving people was good and ought to continue forever. Such famed "antislavery moderates" among the enslaving class as Henry Clay were caught out like that, making explicit proslavery speeches off the cuff in Congress when blindsided by the Missouri Controversy but there was a vocal Slavery Forever contingent going back to the very first Congress. Fierce opposition to proposals to even talk about ways that the rest of the nation could help the South willingly emancipate are telling, as is the nearly as fierce opposition to faculties the US government might develop which could potentially, in the far future be used to work out an emancipation plan.

White Northerners do notice all of this. For most of them, slavery is bad in the abstract but also distant. As long as they feel their hands are personally clean, despite said hands being so deep into complicity and active cooperation that you'd have to go spelunking with a master caver to find their toes, it's not their primary concern. They thus feel quite free to coalition together in parties with enslavers and cut their enslaving friends the usual range of political deals, plus a bit extra. Being primarily antislavery is rare and even among public figures who are so, most of them are mostly fine with having a proslavery wing in their party. They may not love it, but it's how things are. Quitting a party over slavery is basically taking an express exit to political irrelevance until 1854 and not done even by most whites considered fairly strong antislavery men.

Of course that's only the rhetorically antislavery side. Proslavery Northerners, who usually consider themselves sensible and conservative men keenly appreciative of the needs of diverse white Americans to their labor systems and social mores, are not especially rare either. It's very unusual for anyone north of the Mason-Dixon or Ohio River and involved in public life to just say that slavery is awesome and they need more of it, but Yankees are happy to adopt positions not far removed. The most popular of these was to argue for absolute silence. Arguing about slavery was destructive to the national fabric and therefore immoral. This was a sin committed in both sections, to be sure, but white Yankees were almost infinitely worse about it in every respect and must be energetically chastised for "provoking" the white South to extremity. The true course was "moderation" that meant doing nothing at all, except for being ready to cut deals to help slavery spread and entrench.

This is all often accompanied by a reconciliation of free labor, which the white North has come to lionize, with slavery by an argument from what amounts to race pseudoscience: Everyone just knows that white men can't engage in demanding agricultural labor under a tropical sun. They'll outright die of overwork, overheating, malaria, and [insert cause here]. Black Americans, however, grew up in that stuff. They're fitted perfectly for that climate and therefore the work is neither a great hardship to them nor any particular danger. Therefore this is a win-win. If white Southerners are forced to work their own fields -which millions of 'em already did, but this went unacknowledged- then that was tantamount to killing them. Therefore, and for the good of the American and world economies as well as "humanitarian" reasons, slavery must be preserved where it then existed. If more a Yankee lived in the South, and some did and did adopt proslavery views, then they would surely see the truth with their own eyes. Where, these people would ask their fellow Yankees, was your empathy for the white man of the South? Where was your practicality? Where was your good sense? They could go on like this for some time and for it they often reaped generous political rewards, including the presidency.