A year ago, the big U.S. banks were focused on repealing, or at least eliminating large parts of, the Dodd-Frank financial-reform law.

They poured money into the campaign of the Republican presidential nominee, Mitt Romney, and gave generously to opponents of pro-reform Senate candidates Sherrod Brown and Elizabeth Warren.

At the same time, lobbyists devised creative tactics to delay implementation of Dodd-Frank - filing lawsuits, mobilizing international pressure, hiring former regulators, writing opinion articles and comment letters, and commissioning faux research pieces. They failed.

On April 23, I attended a forum organized by American Banker, a trade publication, to discuss the legislative proposal crafted by Brown, an Ohio Democrat, and Sen. David Vitter, a Louisiana Republican. In attendance was a Who's Who of the industry lobby, with all the major groups represented at a senior level, including the Financial Services Forum, the Clearing House and the American Bankers Association. They let it be known that the line from big banks and their allies now is "Let's implement Dodd-Frank."

This sounds like a significant change in rhetoric, but don't fall for it. The reality remains the same - a very powerful lobby is working flat out to ensure that the industry keeps its dangerous, nontransparent and unfair subsidies. Yet the winds are shifting against the megabanks for three main reasons.

First, the Brown-Vitter legislation, which was introduced April 24, changes everything. The news isn't that Brown wants to make the financial system safer. That has been a top priority of his since the spring of 2010. Now he and a Republican co-sponsor have converged on a strong message.

Vitter articulates well the case for ending the implicit subsidies that exist because creditors understand that the government and the Federal Reserve won't allow a megabank to fail. This sensible message resonates across the political spectrum.

Second, small banks are increasingly focused on the ways megabanks have achieved an unfair competitive advantage - primarily through implicit government subsidies.

The most compelling voice at the forum last week was Terry Jorde, a senior executive vice president of the Independent Community Bankers of America. She made clear that small banks are being undermined by the reckless behavior of megabanks that are "too big to fail."

There is no market at work here - just an unfair and inefficient government-subsidy scheme.

The U.S. economy wasn't built on megabanks, and there is no good reason to continue to accept the risks they pose.

As the biggest banks become even larger, they acquire more clout, spreading branches and other largesse across congressional districts.

But for the moment, in all 50 states, community bankers are strong enough - both directly and as leaders in their communities - to effectively stand up to the six largest banks that are at the heart of the problem.

Camden Fine, the chief executive officer of the Independent Community Bankers of America, has made clear that he strongly endorses Brown-Vitter.

Expect to see a lot more community bankers in senators' offices.

Third, what Brown, Vitter and Fine express isn't populist anger, but rather a thought-out plan for making the financial system safer. Read the bill and the section-by-section guidance. Brown-Vitter blends some powerful thinking.

Intellectually, the tide has turned. The dangers of reckless behavior by global megabanks are now understood much more broadly.

And Brown-Vitter provides an appropriate road map for addressing some of the core problems and making the financial system significantly safer.

Simon Johnson is a professor at the MIT Sloan School of Management and a senior fellow at the Peterson Institute for International Economics.