Update:

Here's a summary of Democratic plans:

• Break up the oil companies. Assumption: collusion among an oligopoly is allowing them to keep prices high. There is a lack of competition. Problem: There's already antitrust laws on the books, and a legitimate way to address that concern. Oil drilling and refining is VERY capital-intensive - small companies CANNOT do it cheaper, because they lose "economies of scale" - the ability to do one thing cheaper because you do a whole lot of it.
  
• Windfall profits tax. Assumption: Lots of profit, record-setting profit, even, means oil companies have room to take less profit in order to lower prices for everyone else. Problem: Will we return these profits to the companies during years of very low gas prices, like the late 90's? See point #1 - oil drilling is very capital-intensive. It takes lots of money, involves lots of risk, and is subject to lots of regulation. These things discourage anyone from trying to enter the market (see point #1, if you want competition to lower prices), and artificially lowering their profits will further entrench those that can make very high profits. You can't raise costs and expect prices to hold constant.
  
• Price-gouging legislation. Assumption: We can set a cap on gas prices, but name it in such a way that people hopefully won't think about what happened with gas price caps in the 70's. Problem: A rose by any other name, still means "artificially-low-prices = shortages."

But looking behind the scenes - this is probably just posturing from a Democratic Congress whose approval ratings are cozying up to President Bush.