Yes to both questions.

In the decade prior to the Civil War, there was the heated question of expansion of slavery into Kansas and other new Territories. These evolved violent fights about freedom vs the "state sovereignty" right for the new territories to vote for slavery. That led to violently rigged elections with stuffed ballots to support slavery. Bleeding Kansas was kind of the preliminary battlefield of the Civil War and a microcosm of the issues at hand.

The Confederate Constitution specifically gave the new Confederacy the right to expand into new territories and it also explicitly stated that those new territories must have slavery.

If you look at all of the speeches that states had on the topic of secession and if you read the text of their new constitutions, the biggest justification for secession was the protection of slavery both in existing territories and in new ones as well.

There is a great book which recently came out called "Madness Rules the Hour: The Apostles of Disunion" and this book is a detailed study of the political events which led to war. It is a biography of a dozen leaders who convinced the South to secede.

One of the most important political events was that the radical pro-slavery fire-eater editors of the Charleston Mercury, for lack of a better term, the Fox News of the South, conspired with many Democratic convention delegates to split the Democratic Party.

They demanded that either the Northern States include explicit support for the Dred Scott decision and also the explicit support of the expansion of slavery into the new territories or they would split the Democratic Party into two. They knew this would hand the election to the Republicans which would then be the catalyst to finally get all Southerners to secede. The Northerners voted against that platform and the Southern states walked out and formed a new political party. This turned the two way election into a three way election. Lincoln won and that was the justification the fire-eaters used for immediate secession and war.