My take here:
The ultimate import of the Pledge is as a preemptive act of governing. If the chants of “Speaker Boehner” outside the event announcing the document were premature, they weren’t far-fetched. The Pledge will provide a sheet anchor for Republicans should they take power in a vertiginous sweep, and does voters the civic favor of giving them a preview, in some specificity, of the party’s initial priorities.
The preamble sets out a new iteration of Republicanism. In 1994, the Contract had a Perotista flavor and emphasized first-day institutional reforms of Congress. In 2000, George W. Bush unveiled “compassionate conservatism” as an implicit surrender to big government. In its evocations of the country’s founding documents, the Pledge identifies itself with a constitutional conservatism determined to return government within its proper bounds.