Take a look at the trend in gas prices since the Democrats took over the Congress in January 2007 (data source: Energy Information Administration).
To be sure, prices were trending upward over the first 6 years of the Bush administration with a Republican majority Congress. There was a total rise of 47%, or about 7.8% per year on average. However, in the 18 months since the Democrats took over, with a promise to deliver a comprehensive energy policy and a price per gallon of $2.22, the price of a gallon of gas has risen a further 86% to $4.13 as of the end of June. That annualizes to 57%, or about 4.8% per month on average. Meanwhile they don't want to allow recovery of known domestic reserves, won't entertain increased use of nuclear energy and instead insist on converting our food supply into biofuels which is raising the price of food for people worldwide.
The Congress certainly lost its way under the Republicans but at least they weren't Hell-bent on wrecking the economy. They need to pick up on this issue and hammer away at it if they want any hope of getting back into the majority even staying relevant.