A fascinating piece in the leftist Jacobin magazine details how the formation of the Free Soil and original Republican parties were one of the more aggressively radical projects in American political history, and has some big points about basic political effectiveness:
At each stage of their project, from the Liberty Party to the Free Soil Party and finally the Republican Party, progressively broader coalitions were formed around an emerging ideology of free labor that merged antislavery principles with the economic interests of ordinary Northern whites.
The outer layers of these coalitions attracted voters and politicians who lacked the hard abolitionist principles of the militants, and in a racist society it was inevitable that many of the converts to Free Soil would vaunt theirs as the “true white man’s party.”
But the original nucleus of radicals – despite their own time-bound attitudes – lent the project an inner egalitarian spirit, visible in party campaigns for black suffrage and civil rights across the North. And when the moment of mass radicalization finally arrived in the wake of the Kansas-Nebraska Act, these abolitionists stood triumphantly at the heart of the networks that became the new Republican Party. “Our position is now rather enviable,” wrote Giddings in 1854. “We lead the hosts of freedom.”
Today on the radical left, there is a widespread allergy to political strategy as such. There is far more communion with the countercultural legacy of Garrison than with the political acumen of Frederick Douglass, who by 1852 had become secretary of the Free Soil Party, commenting that “what is morally right is not at all times politically possible.”
The common narrative of the pre-Civil War era focuses on the tension between Northern and Southern states over slavery, but abolition was still an unwelcome idea throughout many parts of the country. In 1844, a mob beat abolitionist John Murray Spear and left him for dead, in Maine.
But in roughly two decades, people like Douglass, Charles Sumner and Abraham Lincoln took that idea from radical to a viable part of the country's political mainstream.
They did it by wading into the muck. The 1860 Republican platform is full of planks (mail! infrastructure! tariffs! homesteading!) that don't have a huge amount to do with the radicals' original goal. Some of these were good ideas in their own right, others were sops to one constituency or another or compromises (framing anti-slavery efforts in Kansas as a belief in state's rights) intended to bring their more sweeping goals a bit closer. There's no reason radicals can't use the boil the frog approach too.
One can only imagine the frustration Douglass felt during all this. He had broken free from torture and slavery only to have to put up with the crap required to get those "outer layer" groups — many of them quite racist — on board. But he did it anyway because it built towards the day when slavery would be wiped out entirely.
So instead of leaving en masse, the radicals stayed in the coalition, and their influence is visible in things like this 1860 campaign song:
They knew exactly where they were heading.
"Incrementalism" gets a lot of flak but unless you can conjure armies or "shut down society" levels of popular support, every approach is going to be incremental.
The abolitionists in the 1840s simply didn't have the numbers or the power to end slavery, and no amount of moral protest or personal righteousness was going to change that. Reversing that situation required getting a bunch of people they didn't exactly agree with into a coalition that wasn't particularly coherent. It worked.