The Congressional Budget Office is a pretty good - but not completely nonpartisan –source of macroeconomic information. This agency tends to line up with the party that controls Congress, but not very strongly. In practice, they many times end up pointing out the unrealistic assumptions of policies.
Its director, Doug Elmendorf, has an (official) blog. Go check out his forecasts for where real GDP is going to go over the next 10 years.
Even though there are variations in the forecasts, they all show substantial growth, and they all turn this terrible, horrible, no good, very bad recession we’re in into just another hiccup.