"Using his veto power, Scott Walker could expand vouchers even more."

The Cap Times reports:

With the stroke of his veto pen, Walker could simply cross out the limits when the budget lands on his desk. Although the broad power of the Wisconsin gubernatorial veto has been curtailed somewhat in the past few decades, it remains an effective way to fundamentally rewrite legislation.... 

The cons are obvious: Reneging on the deal could infuriate Republican moderates in the Senate, including Olsen and Senate President Mike Ellis. Working with the moderate wing of his party in the future might become problematic for Walker. In the run-up to his re-election campaign in 2014, he doesn't need to lose GOP support. 

The pros are simple: It would further endear Walker to the national conservative movement and put another feather in the cap he wears as a likely presidential candidate.