Imagine if U.S. politicians took financial contributions skimmed from the ill-gotten gains of bloody Mexican drug cartels and terrorists.

Imagine further that those who profited off the drug gangs used their murder-tinged cash to lobby the U.S. Congress.

You don’t have to strain yourself, this is not some sordid fantasy concocted by Hollywood to horrify and entertain you. This is the reality created by Wall Street’s finest and our leading politicians.

The latest sorry chapter in Wall Street’s waltz with the drug-dealers is laid out in a report by the Senate Permanent Committee on Investigations. Officials of the British too big to fail bank HSBC acknowledged that despite repeated warnings, they failed to stop drug and terror-tainted deposits from moving through the bank.

According to the report, HSBC, one of the world’s largest banks with a strong U.S. presence, “exposed the U.S. financial system to a wide array of money laundering, drug trafficking, and terrorist financing risks due to poor anti-money laundering controls.”

In 2007 and 2008, the Senate committee found, HSBC moved $7 billion in bulk cash from Mexican to its U.S. operations, even though authorities warned that the money was proceeds from drug sales.

HSBC was doing a thriving business with well-known cash exchange businesses used by the drug cartels known as casas de cambio, despite repeat warnings that they were fronts. Years after other banks had cut them off, HSBC continued to do business with the casas de cambio.

Mexican drug cartels weren’t the only ones taking advantage of HSBC’s lax controls. Middle East bankers with links to Al Queda also found HSBC a hospitable environment in which to conduct business.

You might think that the authorities would have roast HSBC officials on a spit.

Far from it: in 2008, regulators rewarded HSBC with $3.5 billion from taxpayers in a backdoor bailout, in payments funneled to the bank’s U.S. subsidiary through AIG.

Now HSBC’s bankers have been humiliated at a public hearing and the company’s shareholders may be forced to pay as much as $1 billion in fines.

Still, from the bankers’ perspectives, you would have to say money laundering and bailouts have been very, very good to them. Even after they pay the fine, they’d have more than enough to pay for the $125,000 they’ve given to congressional candidates so far this election cycle, and the $5,700 they’ve doled out to Mitt Romney. The left-over laundered money will also help defray the costs of the $900,000 worth of lobbying the bank has done this year.

I’m confident now that the full extent of HSBC’s misdeeds has become known, Romney and the other politicians will want to have nothing to do with this dirty money and will be clamoring to give it to charity.

But just in case it slips their minds in the rush of doing the people’s business, we should help them out. Mitt can provide a good example by being the first to get rid of the drug and terror money.