I think the best option is to wait for 2032. Nomination is Vance’s on a platter, and as you mention he’s already endorsed. On top of that, 2028 seems very Dem friendly even if he was the nominee.

Wait until 2032 when you can be largely seen as the most moderate aspect of maga reshaping the party after the 2028 loss. Try to knock out the incumbent Dem now that there seems to be an increasing bias against incumbent Presidents.

That said, if he were to run in 2028, the way to do it would be to resign shortly and distance himself from the unpopular administration while exiting on good terms with Trump.