Byron York confirmed that it was Republican partisan pressure that forced Gregg to pull out. The idea that a Republican could help give Obama cover on entitlement reform and that he would preside over a big increase in Hispanic representation in the Census was too much for the Rovian partisans. Shill Kristol lets the cat out of the bag:
they were worried that clever “post-partisan” or bipartisan tactics by Obama could split and weaken an already uncertain and demoralized GOP.
Party first. Country always always last. Welcome to today's Republicans.