Politicians don't have as much effect on improving the economy as they think they do--but certainly they can screw things up, especially with accumulating debt. If anything makes our economy really tank, it'll be year upon year of Congress making absolutely no attempt at all to rein in spending ... some years they can't be bothered to pass a budget at all, much less a good one.
RE: book review: The World War 1 Triva Book, by Bill O'Neill