For most of that period, risk on/risk off mentality plus a nice dose of QE 1,2 and 3 have been the major forces affecting the dollar. In recent weeks there has been another factor at play though which has been interesting to watch. Ever since Romney's strong performance at the first presidential debate, the market has started to price in the possibility that he could actually win. This would have big implications for the Federal Reserve, QE and the dollar, because most expect Romney to push for an end to QE. As such, the dollar has started to trade with some correlation to the Romney intrade contract. In the last few weeks, when Romney's odds of winning increase, the dollar (measured by DXY) increases as well.
Importantly, most people seem to think that a Romney presidency would be a positive for equity markets; however, a Romney presidency would likely mean a stronger dollar, which could mean lower equity prices if the correlation holds.