Remember that only a few generations ago, Lincoln invaded the states of the south to maintain tax revenue. Were a state to peacefully secede, I feel confident that the current president (Republican or Democrat), would react the same.
I'm no fan of President Lincoln, but you might enjoy reading about Fort Sumptner.
And as to our "current president (Republican or Democrat), would react the same. To keep a state in the Union". Well that is in their job description to do just that.