No, he was not a liberal. He was the ultimate CONSERVATIVE. He waged a war in order to preserve (conserve) the United States, hence the term “UNION”. He also fought to conserve the Constitution.
Here is an actual quote from Mr Lincoln (R):
“My paramount object in this struggle is to save the Union, and is not either to save or to destroy slavery. If I could save the Union without freeing any slave I would do it, and if I could save it by freeing all the slaves I would do it; and if I could save it by freeing some and leaving others alone I would also do that. What I do about slavery, and the colored race, I do because I believe it helps to save the Union; and what I forbear, I forbear because I do not believe it would help to save the Union.”
He also did say this:
“As I would not be a slave, so I would not be a master. This expresses my idea of democracy.”
Also, this:
“Whenever I hear anyone arguing for slavery, I feel a strong impulse to see it tried on him personally.”