The Deficit Was Not Ballooning Until the Economy Collapsed by Dean Baker

Actually the deficits were not ballooning until the collapse of the housing bubble crashed the economy in 2008. The budget deficit in 2007 was 1.2 percent of GDP and the debt to GDP ratio was falling. The Congressional Budget Office projected that it would stay in this neighborhood for another decade or so even if the Bush tax cuts did not expire. The reason that the deficit became large and the debt to GDP ratio started to rise was that the collapse of the economy cost the government hundreds of billion in tax revenue annually and led to hundreds of billions of additional expenditures for unemployment benefits and other programs to counteract the impact of the downturn.  

While the Bush tax cuts may have been bad policy, in fact they were affordable in the context of an economy that was near full employment. If the collapse of the housing bubble had not sank the economy, there would be little issue about the sustainability of the debt.