There was no mandate for UPA in the first place in last 2004 national election. UPA was a post poll arrangement which faught against each other. Many UPA constituents were part of NDA - like DMK, PMK, Paswan etc.
BJP got just 6 fewer seats than Cong. BJP lost ALL metro seats except 3, because urban people were kind of assured that BJP led NDA was coming back. So, we are not going to make the same mistake again:)-