[Fury]

I make this point often as well. I tell them that if the war was to free the slaves, they could have started in Maryland where their supply lines would have been much shorter.

If this had occurred, was there a concern that Maryland and potentially other border states would have seceded and joined the Confederacy?

[DiogenesLamp]

Very much so. I believe Lincoln even stated this explicitly.

The last thing he needed was to drive Missouri, Kentucky, Maryland, Delaware and West Virginia out of his coalition and move their support over to the CSA.

He did specifically say that if he lost Kentucky, he lost the whole thing.

A lot of people saw Lincoln as pulling a "bait and switch."

[DiogenesLamp]

Also, were it not for military intervention in both Maryland and Missouri, they likely would have joined the CSA anyway.

In Maryland they arrested all the pro-secession legislators, and in Missouri, they made them flee the capitol.