In a stunning reversal, Senate Minority Leader Mitch McConnell (R-K.Y.) is urging the Senate G.O.P. caucus to vote against the bipartisan border security and foreign defense aid package. It comes after spending weeks helping a bipartisan group of senators craft it, and just hours after he spoke in favor of the legislation. The development was reported by Punchbowl News’ Jake Sherman, who said McConnell’s announcement came in a closed-door Republican strategy session with his colleagues. The proposed bill, released over the weekend after negotiations between Sens. Chris Murphy (D-C.T.), Kyrsten…