Answer: As a Republican, Lincoln opposed the expansion of slavery and his victory convinced many Southern states to secede.
Explanation:
One of the primary reasons the Republican party was formed was to limit the spread and if possible, outlaw slavery in the United States.
When Abraham Lincoln became the first President to be elected under the party banner, the Southern states who for a long time had felt marginalized by the non-slavery supporting North, decided to secede.
They did this because they knew that with a Republican in power, anti-slavery rhetoric would be pushed on them and they did not want this. They wanted to practice slavery unimpeded.
