Washington’s odd duo of Sherrod Brown and David Vitter on Wednesday hope to trigger an existential change, one that could even prompt some breakups, within the nation’s biggest banks.

The senators — one a liberal Ohio Democrat and one a conservative Louisiana Republican — will do so by unveiling their long-awaited “too-big-to-fail” bill, whose concept already got unanimous support in a non-binding Senate resolution. The basic idea is that if the federal government stands ready to bail out banks deemed too economically vital to fail, and if that guarantee gives those banks a financial advantage against smaller competitors, those megabanks had better curtail what critics see as reckless risk-taking.