[Jack]

Actually, the blowout preventer had a back up switch, which failed during a test a few weeks before the blowout. Instead of taking steps to remedy that, or shutting down until it was fixed, that problem was ignored.
In addition, during the same test a few weeks before the blowout, the rubber gasket that is supposed to shut down the well if something goes wrong, broke down. This was detected when chunks of rubber appeared in the drilling mud- and that was ignored, too.
BP actually isn't a very major player in political contributions, compared to many energy companies. BP spent 3.2 million in contributions, over the span of the last 20 years. Obama got 77, 000$ in contributions from BP, during that time. To put those numbers in some perspective, in the 2000 election cycle, Bush got 979,000$ from Enron.
The real lack of oversight on the oil companies can be traced to the MMA, (Minerals and Mining Agency) part of the department of the Interior. Officials at that agency were far too close to industry lobbyists, accepting gifts, etc. A lot of tests, safety procedures, etc, were let slide by those officials.
Congress can pass all the regulations it wants, but if they aren't enforced, they do no good.