I've heard some pundits describe a president as being similar to an NFL quarterback. When things are going good, both get too much credit. When things are going badly, both get too much blame.

When the economy was booming in the 1990s, plenty of people from the Democrat side rushed to give Clinton the credit. Likewise, when the economy slowed down in 2000 and entered a recession in 2001, they were quick to blame it on Bush, calling it the "Bush Economy". Now that the economy is showing good signs of turning around, those same people would rather slit their own throats as to admit anything Bush did could've had a positive impact.

The economic policies a president tries to enact can have a significant impact on the economy, assuming he can get the policies enacted by Congress and he isn't kneecapped by the Federal Reserve. After all, a president can advocate low interest rates, but it's the Fed that makes it happen. Similarly, a president can call for tax cuts but they have to be enacted by Congress.

It seems to me that it's more likely that the government will do damage to the economy than to make things better. New laws, new regulations, new taxes, all of these things tend to have bad economic impacts, but passing these things are the lifeblood of government.