He was a former Whig. The Whigs were divided on whether or not to support slavery. The party dissolved, and the anti-slavery Whigs in the North created a new party to oppose slavery and they called themselves Republicans. Lincoln was one of these republicans. In 1860, they nominated Abraham Lincoln to run for President.
He said he would not interfere with states who were pro-slavery. However, after he was elected, many southern states decided he was too anti-slavery, and so they decided they would secede from the union and formed the Confederate States of America. This caused Abraham Lincoln to use Federal troops to fight to preserve the nation. This was good. The effort would result in the deaths of 620,000 soldiers (bad), but the effort would eventually succeed (good).
Sure, he was a liberal in that he wanted to end slavery, a change that would have been quite radical considering slavery had existed long before the birth of the nation. However, this change would also move the nation more in line with the founding intentions of "all men are created equal." It would also make the United States the
To be honest, it doesn't matter if freeing the slaves and giving them equal rights was a liberal or conservative act: it was the right thing to do. For this, we rank Lincoln high on our ranking of Presidents. Okay, that's not arguable. And, I'm sure few would argue with me. Well, I known there are libertarians who rank Lincoln on the bottom of their rankings.
That success aside, he was not a conservative. Here is the evidence.
1. He raised taxes. Prior to the passage of the 16th Amendment in 1909 and ratification in 1913, the only means the Federal government had for raising revenue was through custom taxes or tariffs. There was no income tax. If the Federal government needed to increase revenue, it was up to the states to raise money. This was a means of preserving state sovereignty. Lincoln changed this when he signed the Civil War Revenue Act of 1861 that created an income tax of 3% on all income over $800. This was the nations first income tax. It was supposed to expire in ten years.
Later, on July 1, 1862, Lincoln signed the Revenue Act that created the Commissioner of Revenue position. This commissioner had the power to impose even more taxes. To run the program, Lincoln created the Bureau of Internal Revenue.
2. He created more government jobs. Along with increasing the power of government, he also increased the size of government. Within the next six months, over 4,000 government jobs were created to make sure citizens paid the taxes and to prosecute those who did not.
3. He gave the Federal government power over the states, especially in regards to slavery. This was opposed to democrats of the time, who preferred states rights over social justice. Democrats favored limited government over big government.
Lincoln wanted to enforce social justice on the nation, and thereby democrat claims of "state's rights" and forced states to respect the natural rights of blacks. This includes the 13th amendment to abolish slavery. I'm not saying this was bad (by God, no I'm not saying that). I'm just saying this was a liberal change, not a conservative one. It was radical social change.
As a side note here, what we now refer to as conservative was called liberal back then. The term liberal would later be absconded by the progressive movement, and so now liberal means the opposite of its initial intention. Today's liberals are also called progressives, and Lincoln was a social liberal progressive, if we were to use today's terms. He probably would be a democrat. A liberal. A neo-socialist. This is because he used big government to enforce his social agenda.
Anyway, Lincoln's republican party was in favor of a large central government and collective rights, similar to modern liberals.
I do not think I need to go into any further detail regarding Abraham Lincoln, as I would imagine any respectable American over the age of 8 knows who he is and what he did for the nation. He was a great President, perhaps the greatest. He kept the nation together during difficult times, and changed the nation so that it was closer to the founding intentions by freeing the slaves and ensuring that their natural rights would be preserved.
He said in his Gettysburg Address in 1863 that he guaranteed a "government of the people by the people for the people, shall not perish from the earth." Thanks to the bravery of this brave and melancholy President the nation continued and more people were granted liberties. That, I would say, is a great achievement, making him the second greatest President of all time.