When Gov. Ed Rendell floated his budget proposal in February, Pennsylvania’s economic forecasting consultant said the slack economy would rebound in the second half of 2008.

Then the firm, Global Insight, grew more pessimistic as the economy worsened and issued another opinion to its client. It said things might begin turning around in the first half of 2009.

‘‘I’m not going to tell you that we are absolutely certain that things won’t get worse,’‘ Michael Masch, the chief budget adviser to Gov. Ed Rendell, said Thursday. ‘‘The best advice we can purchase is telling us they’re not going to get dramatically worse, based on the what the smartest people in America who study this stuff are telling them.’‘