RE LINCOLN

The Republican platform for 1860 certainly contemplated attacking the slave holding states, especially those that seceded from the Republican held Union.

You can read the Republican platform for 1860 for yourself.

Question: had a non slaveholding state chosen to side with the seceding states and secede, on the principle of a right in the several states of secession, which they all clearly had thought that they had, what would have been the Republican Party's, and Lincoln's, position on that secession?

On the other hand, one had several slave holding but non seceding states.  How do you think they were treated? How should they have been treated by the various factions? How, under the Platform?

The whole thing politically was a disaster. 

See border states (American Civil War) Wikipedia:

"Border secessionists paid less attention to the slavery issue in 1861, since their states' economies were based more on trade with the North than on cotton. Their main concern in 1861 was federal coercion; some residents viewed Lincoln's call to arms as a repudiation of the American traditions of states rights, democracy, liberty, and a republican form of government. Secessionists insisted that Washington had usurped illegitimate powers in defiance of the Constitution, and thereby had lost its legitimacy."

Maryland:

"Union troops had to go through Maryland to reach the national capital at Washington, D.C. Had Maryland also joined the Confederacy, Washington, D.C. would have been surrounded. There was popular support for the Confederacy in Baltimore, Southern Maryland, and the Eastern Shore, the latter two areas with numerous slaveholders and slaves. Baltimore was strongly tied to the cotton trade and related businesses of the South. The Maryland Legislature rejected secession in the spring of 1861, though it refused to reopen rail links with the North. It requested that Union troops be removed from Maryland.^[24] The state legislature did not want to secede, but it also did not want to aid in killing southern neighbors in order to force them back into the Union.^[25] Maryland's wish for neutrality within the Union was a major obstacle given Lincoln's desire to force the South back into the Union militarily.

To protect the national capital Lincoln suspended habeas corpus, and imprisoned without charges or trials one sitting U.S. Congressman as well the mayor, police chief, entire Board of Police, and the city council of Baltimore.^[26] Chief Justice Roger Taney, acting only as a circuit judge, ruled on June 4, 1861 in ex parte Merryman that Lincoln's suspension of habeas corpus was unconstitutional, but the president ignored the ruling in order to meet a national emergency. On September 17, 1861, the day the legislature reconvened, federal troops arrested without charge twenty-seven state legislators (one-third of the Maryland General Assembly).^[27][28] They were held temporarily at Fort McHenry, and later released when Maryland was secured for the Union. Because a large part of the legislature was now imprisoned, the session was canceled and representatives did not considered any additional anti-war measures. The song "Maryland, My Maryland" was written to attack Lincoln's action in blocking pro-Confederate elements. Maryland contributed troops to both the Union (60,000), and the Confederate (25,000) armies.

Maryland adopted a new state constitution in 1864 that prohibited slavery, thus emancipating all remaining slaves in the state."