At their massive downtown Chicago rally today, the National Nurses United union stuck with a script they developed prior to President Barack Obama relocating this weekend’s G8 economic summit from Chicago to Camp David – advocacy for developed nations to impose a tax on financial transactions.

A ‘Robin Hood’ tax, so named because it would presumably take money from rich investors and give it to people in need of social services, is not a marginal policy idea. The European Union may soon enact the tax. In the U.S., Obama opposes the tax, but many progressive members of Congress support it.

Arguably the most energetic rally moment was nurses, dressed like Robin Hood, doing a version of Martha Reeves & The Vandelas “Dancing in the Street,” changing the chorus to “It’s time to tax Wall Street.”

Here is video of the song:

U.S. politics are different. The White House states such a tax would disrupt the volume of Wall Street trade, arguing that it would be easy for big banks to game the tax – costing small investors in the end.

But the Congressional Progressive Caucus – made of 76 of the U.S. House’s most liberal members – does actively push for the tax. Their proposed fiscal year 2012 budget creates a financial transaction tax that would generate the federal government $849 billion over the next decade.