Definitely FDR. A 25% reduction in spending takes the cake.
This was not a lie. There is reason to believe he really had no clue of what he'd be doing - honestly, nobody had a clue then, nor, really, has it now what should have been done. The lie is when you say something knowing when you are saying it that you aren't going to do it or that it is not true. That he eventually decided on a course of action he did might have been for the good or for the bad (actually, even now nobody really knows the answer to this, though pretty much everyone is convinced that a major reduction of spending then would have been a disaster), but re-analyzing the situation and changing the policies accordingly does not make original promises lies, unless you can show he never intended to do what he claimed he'd do.
Assuming he was convinced in early 1933 that sticking to his promise was a disastrous policy, being true to his promises meant not performing his duty. Within the framework of the US Constitution he could not run a new election under a new program. Perhaps, that's an argument for a parliamentary system (a British Prime-Minister could have called a new election) or a direct democracy (a Swiss or Californian gov't could call a referendum).
