John McCain says he will balance the budget in four years. I'm aware of no credible economic analyst who believes that's possible, given the enormous tax breaks McCain has promised.
But it's worth mentioning that balancing the budget in four years shouldn't be the goal. In the short term, we need deficits in order to stimulate the flagging economy. And, over the medium term, we need to spend money on the sorts of investments--like public works, energy independence, and health care reform--that will make our economy more productive in the future.
Don't take my word for it. Here's another Nobel Prize-winning economist, Joseph Stiglitz:
...we should never actually focus just on deficits, but on broader economic concepts. The deficit is only one of several accounting frameworks. And it's probably not the best way of assessing either the fiscal position of the economy or its economic position. ...
...the country has a large number of priorities, real priorities. ... the challenge of globalization, the growing inequality, the health care crisis. But there are others such as our problems of energy and climate change. Meeting these, some of these, will require spending money that might create the larger deficit. ... if this money is spent well; it does make sense to do that, even if it led to a greater deficit.
...the current state of the economy is such that deficit reduction, done the wrong way, could have a large macroeconomic cost. So that if you put it another way, if we spend money the right way, it could have two benefits, the direct benefit as well as the benefits that come from macroeconomic stimulation.