The Republican Party was founded in 1854 in Wisconsin. At the time the U.S. had a one party system. The Democrat Party controlled the government. The priority of the Democrat Party was the expansion of a slave based economy.
The Republican Party had its main support from the tradesmen and small farmers in the Midwest. The Democrats had recently passed the Kansas Nebraska act for the sole purpose of expanding the slave economy into the Midwest and the west. Most Americans did not want have to earn their livelihood and support their families in a slave based system with a few wealthy slave holders and the rest of the people struggling in extreme poverty.
That is why the Republican Party grew so quickly.
The South at the time had a few wealthy plantation owners. The majority of the people lived a poor and backward life with little or no opportunity. The innovation and advancement came in the north.
Read about the south in the winter and spring of 1865. Desertion from the army was common. There were riots against the government. There was little support for the Confederacy.
Secession was pushed through very quickly by a small group. It was not debated. It did not have wide support. Those who pushed secession falsely claimed that no one would fight to preserve the union and that an independent Confederacy could be easily acheived without any struggle. Those Democrat politicians who pushed secession did enormous harm to the average southerner. People lost their lives, their wealth and their land.
“Secession was pushed through very quickly by a small group. It was not debated. It did not have wide support.”
That’s probably why generals McClellan, Pope, Hooker, Burnside, and Grant were able to quickly walk into Richmond unopposed with little loss of life in the Union armies.
The whigs self destructed, and much of the new Republican party was made from former whigs.
The Democrat Party controlled the government. The priority of the Democrat Party was the expansion of a slave based economy.
This gets repeated a lot, but it isn't really accurate. The Democrats did want slavery expanded to all the territories, but not so much because there was any profit to be made from slavery in the territories, but because when territories turned into states, those states would side with the Slave states in congress, and thereby keep the North Eastern coalition from enacting any more laws damaging to the interests of the existing slave states.
It was about controlling congress, and not so much about expanding slavery as people have been claiming since the 1840s. Here is why slavery wasn't going to expand to any significant degree. It simply wasn't feasible.
Here is a modern map of cotton growing in the US. Everything in west Texas and further west was not possible in the later half of the 1800s, because it requires modern irrigation systems to get cotton to grow in those states. It couldn't have been done in the 1870s.

So once you toss out West Texas, New Mexico, Arizona, and Southern California, what you are left with is the areas in which it might have been possible to grow cotton.
So do you see any place you could have put a slave plantation in the territories? There isn't any. So how are you going to get "expansion" into the territories?
You weren't. Oh yes, you might have the occasional entrepreneur with a few slaves trying to do something in those territory states, but it would never be anything of any major significance. Slavery was only profitable growing cotton or tobacco, and not much else. Without the ability to grow those cash crops, you could not have had any significant slave presence in any of the territories.
According to the Wikipedia entry under "New Mexico Territory", it says that there was something like 12 slaves in the entire territory.
Most Americans did not want have to earn their livelihood and support their families in a slave based system with a few wealthy slave holders and the rest of the people struggling in extreme poverty.
And this is an important point. We have been taught during our lives that northern Americans opposed slavery because it was morally wrong, and unfair to black people, but the real truth is that the vast majority of northern Americans opposed slavery because they didn't want slaves working at jobs they needed for income. They didn't actually care about the slaves at all. They cared about the threat slaves posed to their livelihood.
There objections weren't moral, they were economic. Except for the nutty Puritans and other abolitionists, the vast majority of Americans didn't like it because they didn't want to have to compete against free labor for jobs.
Read about the south in the winter and spring of 1865. Desertion from the army was common. There were riots against the government. There was little support for the Confederacy.
Having about 20% of your young male population killed by invaders would tend to make you unhappy with the existing state of affairs.
Secession was pushed through very quickly by a small group. It was not debated. It did not have wide support.
Sounds exactly like what the founders did in the Revolutionary war. Was it okay when they did it back in 1776?
Those Democrat politicians who pushed secession did enormous harm to the average southerner.
You need to put the blame on the people who are actually to blame for that loss of life and property. It was the *INVADERS* that killed those people. Wanting to be left alone is not sufficient cause for people to send armies into your state to murder you.
False. There was a 2 party system. The Republican party displaced the Whig Party.
The South at the time had a few wealthy plantation owners. The majority of the people lived a poor and backward life with little or no opportunity. The innovation and advancement came in the north.
You grossly overstate the economic divide in the Southern states. There were plenty of people between dirt poor and mint julep sipping plantation owners. There was a thriving middle class of tradesmen, professionals and middling farmers.
Read about the south in the winter and spring of 1865. Desertion from the army was common. There were riots against the government. There was little support for the Confederacy.
By 1865 desertions were high. There was widespread hunger and the overstretched logistics system supporting the Confederate Army was breaking down. I emphasize that lots and lots of Yankees were mowed down in the last year of the war though - so obviously plenty of men remained in the Confederate ranks. The Union army had a major desertion problem too by the way.
Secession was pushed through very quickly by a small group. It was not debated. It did not have wide support.
False. It had been discussed and debated for years. It had widespread support. Again several states held referendums. Several others elected representatives to secession conventions. Everybody knew what plank various representatives to those conventions were running on. They knew they were voting for pro secession candidates.
Those who pushed secession falsely claimed that no one would fight to preserve the union and that an independent Confederacy could be easily acheived without any struggle. Those Democrat politicians who pushed secession did enormous harm to the average southerner. People lost their lives, their wealth and their land.
and conversely, Northerners thought few would fight to defend an independent South and that war would be quick and cheap. That proved disastrously wrong. Venal Republican Party politicians and their fatcat corporate supporters did a lot of harm to average Northerners by pushing too hard for other people's (ie Southerners') money setting terms most Southerners were not willing to live with. A helluva lot of Northern men got killed and mangled as a result of the war of aggression they waged to keep their cash cow from leaving.