This year, some Senators have proposed breaking up the traditional red team-blue team State of the Union seating chart and having Democrats and Republicans intermingle their seating. It's a completely symbolic move, a cost-free way to signal bipartisanship that requires no substantive policy compromise. Who could possibly be against that? Mitch McConnell, that's who:

Senate Minority Leader Mitch McConnell isn’t looking for a date for Tuesday night’s State of the Union address.
While other lawmakers are firming up plans to sit next to members of the opposite party, the Kentucky Republican said during an appearance on Fox News Sunday that he’s “going to sit where I usually sit” – at the Republicans’ leadership table – but others are welcome to sit wherever and with whomever they want.

This is more evidence for my theory that McConnell is worried about his right flank in a primary or leadership challenge and acgtively looking to signal hostility to Democrats at every opportunity.