Just say you "support the Republican nominee" and be done with it.
Same thing as saying you endorse Romney.
Not if you wait until Romney has 1144 delegates and thus the nomination. Doing so beforehand is supporting Romney; doing so afterhand is supporting the Republican nominee.
At this point in the game, with everyone knowing full well that Romney is now the nominee, with reaching 1144 only a formaility, only a political coward would wait until Romney reaches 1144, then says something so obviously patronizing and stupid as
I support the Republican nominee.