Even though Obama is outspoken in his support for charters, push-back comes from new proposed charter schools being linked with privatization and school closings. Recent studies in Chicago found that charters were doing no better than the schools they were supposed to replace.
Another reason for resistance to lifting the cap is that there are still unused charter slots in the suburbs and downstate 13 years after the charter law was enacted and the initial cap set. It seems that there's little demand outside of Chicago and little political incentive to shift funds away from struggling urban schools in these times of crises and budget cuts.
In Ohio, Gov. Strickland and Democratic legislators are strongly opposed to privately-managed charters, despite Obama's call for more, and they're reducing their line in the state funding budget by 20%. It could be because Ohio's charters are some of the worst in the nation in a state where there's little accountability over their quality.
From the Cleveland Plain Dealer:
Strickland complains that for-profit companies that manage charter schools are blinded by the money, showing little interest in teaching children.