Donald J. Trump has won the presidency of the United States, due to strong support among white voters. This is a remarkable turn of events, and it only gets more remarkable when you think back to how the Republican Party began its existence: fighting against the expansion of slavery.
Over the past century and a half, though, the party of Abraham Lincoln has changed dramatically. It went from a party that was racially progressive for its times, to one that gets little support from nonwhite voters. And it went from a Northern-only party, to one that dominates the South. Here's how it happened.
I. From an anti-slavery party to a pro-business party
1) The Republican Party was founded to oppose the "Slave Power"
For the first half-century after the United States’ founding, slavery was only one of many issues in the country’s politics, and usually a relatively minor issue at that. The American South based its economy on the enslavement of millions, and the two major parties — which by the 1850s were the Democrats and the Whigs — were willing to let the Southern states be.
But when the US started admitting more and more Western states to the Union, the country had to decide whether those new states should allow slavery or not. And this was an enormously consequential question, because the more slave states there were, the easier it would be for the slaveholding states to get their way in the Senate and the Electoral College.
Now, the issue here wasn’t that Northern politicians were desperate to abolish slavery in the South immediately, apart from a few radical crusaders. The real concern was that Northerners feared the "Slave Power" — the South — would become a cabal that would utterly dominate US politics, instituting slavery wherever they could and cutting off opportunity for free white laborers, as historian Heather Cox Richardson writes in her book To Make Men Free.
By 1854, in the face of intense controversy over whether Kansas and Nebraska would enter the Union as free or slave states, the Whig Party, which had been divided on the issue, collapsed. And remarkably quickly, a new, entirely Northern party sprang up to take its place.
While not calling for abolishing slavery where it already existed, and certainly not calling for racial equality, this new party would be resolutely opposed to expanding slavery any further. Its supporters and sympathizers won an impressive share of seats in Congress, and it became known as the Republican Party.