SAN FRANCISCO (MarketWatch) — Imagine if the big banks could design a dream ticket from today’s crop of politicians. Could it do any better than the Republican tandem of former Massachusetts Gov. Mitt Romney and Rep. Paul Ryan of Wisconsin?

Romney’s experience at Bain Capital makes him probably the most investment-friendly candidate in history. And so far he’s delivered, promising to keep tax breaks for investors and the wealthiest Americans.

That may be a good or bad idea depending on your political persuasion. But it’s undoubtedly good for Wall Street because it creates a financial incentive for customers to participate.

Ryan, chosen by Romney on Saturday as his running mate, may be an even better choice from the industry’s perspective. While the seven-term congressman has become popular as the Republican Party’s most visible spending hawk, that’s not what appeals to Wall Street (which actually prefers high levels of government spending).

No, Wall Street loves Ryan because he’s bringing back an old idea: he wants to privatize Social Security.

In 2005, Ryan proposed the Social Security Personal Savings Guarantee and Prosperity Act. Under the proposal, workers would have been able to funnel at least half of their Social Security deduction into a private account. The account would have been managed by the Social Security Administration and invested in a portfolio made up of anywhere between 50% and 80% stocks. The rest would have been in bonds.

Again, you may agree with this proposal because you believe like Ryan that it will “save” the program for future Americans. Or, you might disagree with it on the grounds that the program will remain “underfunded.”

Regardless of your position, there’s no denying who it would benefit: big brokerages.

That’s because even though SSA would “manage” the program, it would need Wall Street’s help: brokers, market-makers, specialists, you name it. Suddenly the financial industry would be getting up to $340 billion, half of Social Security’s 2011 revenue, for fees, commissions and other value-added services.

One study predicted that by 2050 every stock and bond in the U.S. market would be owned by Social Security.

You can almost hear Wall Street slobbering.

The problem with the proposal, as with many “privatization” proposals, was the loss of cash to the federal government. The government, after all, uses Social Security money to pay for stuff and then writes an IOU to the taxpayers.

Another problem, Americans have just lived through the worst financial crisis and market plunge since the Great Depression. At the height of the crisis in 2008, 62% opposed privatization, though it’s recently made a comeback, with 52% support in a CNN/ORC poll.

Ryan’s plan and former President George W. Bush’s plan both lost momentum.

In the years that have followed, Ryan has focused less on Social Security and more on cutting federal spending across the board. And recently he’s voiced some support for separating commercial banking from investment banking, telling an interviewer “Don’t let banks use their customers money to do anything other than traditional banking.”

But that’s just a drop in Ryan’s pro-Wall Street ocean. He voted for the bank bailouts in 2008. He voted against a bill in 2009 what would have modified bankruptcy rules so homeowners could avoid foreclosure. And last year, he voted for a bill that would have shuttered the Home Affordable Mortgage Program.

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Given his voting record, lawmaking record and his campaign finances it would be easy to conclude Ryan is in the pocket of the banks.

During the current election cycle Ryan has taken $530,900 from banks, brokerages and insurance industries, about 12% of his $4.7 million in campaign funds. Among his top 10 donors are individuals and political action committees from Wells Fargo & Co. WFC, -2.35% , Goldman Sachs Group Inc. GS, -1.14% and UBS AG UBS, -0.54% , according to OpenSecrets.org.

That may seem like a lot from the financial industry, but it’s really not. Wall Street has spent $128 million so far on this election cycle, more than any other industry.

Everyone who has aspirations of elected office in Washington is taking from the big banks. Vice President Joe Biden took $1.5 million from Wall Street between 2001 and 2006. It’s not fair to single out Ryan.

Still, Wall Street couldn’t be more excited with Romney’s choice. By picking him, Romney and the party establishment are signaling that privatization, as unpopular as it may be, hasn’t been abandoned.

Privatizing Social Security has long been the Holy Grail of Wall Street. With Paul Ryan on the ticket, Republicans in control of the House of Representatives and memories of 2008’s crash fading, there’s a chance that less than a decade after nearly wrecking the global economy, big financial interests could get the power to finish the job.