If Mitt Romney challenges Jeb Bush, Rand Paul stands to gain

If he does, he certainly won’t be assured of the nomination. Republicans will probably have more attractive alternatives in 2016 than they did four years earlier.

But Mr. Romney would be a central player in the nomination contest. He would enter with a modest base of pre-existing support (some polls show him with a nominal if underwhelming lead) and extremely high name recognition. He has the wide network of contacts and donors necessary to build and finance a strong political operation.

There is even a scenario in which Mr. Romney goes on to win the nomination. He would position himself to the right of Jeb Bush, but still have enough support from the establishment and business-friendly conservatives to prevail in a national contest.