Think of the Republican primary field as a series of lanes. In this race, there are four of them: Establishment, Tea Party, Social Conservative and Libertarian. The four lanes are not of equal size: Establishment is the biggest followed by Tea Party, Social Conservative and then Libertarian. (I could be convinced that Libertarian is slightly larger than Social Conservative, but it’s close.)

Obviously the fight for the top spot in the Establishment lane is very crowded with Bush and possibly Wisconsin Gov. Scott Walker leading at the moment. Ditto the Social Conservative lane with former Arkansas Gov. Mike Huckabee, Ben Carson and Rick Santorum all pushing hard there. The Libertarian lane is all Kentucky Sen. Rand Paul’s but, as I noted above, it’s still not that big.

Which leaves the Tea Party lane, which is both relatively large and entirely Cruz’s. While Paul looked as though he might try to fight Cruz for supremacy in that lane at one time, it’s clear from his recent moves that the Kentucky senator is trying to become a player in a bunch of lanes, including Social Conservative and Establishment.