John McCain.
Before the inauguration. Not now.
Why only before? There is no right to run for nor to be elected President. What specific injury did McCain suffer? No McCain would not have had standing either, although it is nice to pretend that he would have, if only he'd acted "in time". But alas, he didn't, and so the case is now moot. Somewhat like Article II, Section 1, clause 5 of the Constitution.