Romney's rivals conceding Arizona to him....for now

[Mr. Morden]

Gingrich is already focusing on Super Tuesday states and Santorum on Michigan plus Super Tuesday states.  Paul will probably play in Michigan as well, since you only need to get 15% to at least get some delegates.  But Arizona is statewide WTA, and it looks like, at least for the moment, all of Romney's rivals think challenging him there is hopeless, and they're planning to concede it:

http://decoded.nationaljournal.com/2012/02/romneys-rivals-seem-content-to.php

Obviously, this might still change, but for now it looks like Arizonans might be spared two solid weeks of nonstop campaign ads.

[Mr. Morden]

Romney just needs to hold on until all the states are WTA,

There is no such point at which all states are WTA.  The only pure statewide WTA states and territories are:

http://twitter.com/#!/FHQ/status/167416214438686722

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Everything else is either WTA by congressional district, proportional representation, or some kind of hybrid, with the hybrid category being the most common.