I agree, except that the formation of the Republican Party was a good deal more complicated than the Whig Party + abolitionists.
The Whig Party was national, so its southern members went into the southern wing of the Democratic Party, often holding their noses, when the Party fell apart. Few of the northern Whigs could stomach joining the northern Democrats because of their slavery-enabling platforms. So they formed the basis of the Free Soil Party and then the Republican Party.
But the Grand New Party also had strong elements from the also-disintegrating American (Know-Nothing) Party (southern Americans also joined the Democrats) and northern Democrats who just couldn’t stomach (like the northern Whigs) the sucking up of their leaders to the slavers. The abolitionists were initially a minor force, limited mainly to New England. A LOT less important than defecting Democrats, for instance.
The 1850s were a truly fascinating period in American political history. Things were firing off in all directions till Douglass and Taney stabilized things by trying to take slavery out of the political picture. Almost exactly what was tried with abortion in Roe. Worked even less well, of course.
That system wasn't built overnight.
The Hughes family orchards in Southern Indiana were used regularly as a burial site for slave catchers who thought they could get away with invading the lower midwest and catching freed slaves to take back South. When I was a young child one of my great aunts was walking me around a remnant of those orchards and she said "They say that wherever there's a pile of rocks there's a slave catcher in there" and I looked around and that orchard had lots of piles of rocks. Only years later did I come to understand what had been going on. There was also a post Civil War Freedman's school in the area that prepared former slaves for independent farming or working as hired hands.
Most likely I'm one of the few Freepers who knows of a relative prosecuted and convicted of violating the fugitive slave act but I'm sure there are others. That act was passed to placate Southerners ~ on September 18, 1850. The Abos were on the march.
BTW, the RadicalRepublicans, ardent abolitionists, were a known political force within the Republican party by 1854 ~ the same year the party was ounded as an anti-slavery party.
The idea the Abolitionist movement didn't participate in the Republican party is not well grounded!