The House Financial Services Committee is holding a hearing on the reauthorization of the Export-Import Bank of the United States, the usually-obscure government agency that subsidizes U.S. exports with taxpayer-backed loan guarantees to foreign buyers.

This morning, a line to get into the hearing room stretched to the end of the hall, turned the corner and went to the end of the next hall. Would-be attendees are being directed to an overflow room.

Ex-Im officials, flight attendants, pilots, manufacturer unions and K Street lobbyists populate the crowd.

It's a stark difference from Ex-Im hearings past.

Two years ago, I attended the Ex-Im markup. The hearing lasted less than half an hour. Committee chairman Rep. Gary Miller introduced his substitute bill, which passed on two uncontested voice votes. Then he adjourned. A few lobbyists high-fived. I ran off to Hains Point and played nine holes.

Last decade, Ex-Im's reauthorization passed both chambers on unanimous consent. When I speak about Ex-Im, typically, nobody has ever heard of the agency.

What's changed? Why has Ex-Im become a controversial issue?

Mostly, it's the Tea Party's populism.

The 2008 bailouts infuriated many Americans. President Obama passed Obamacare with the backing of the hospital and drug lobby. The business lobby helped pass the stimulus bill.

Suddenly, many grassroots conservatives were railing against corporate welfare. Rand Paul won his Senate primary in 2010 in part by railing against D.C. lobbyists.

In 2012, 19 Senate Republicans and more than 90 House Republicans voted against reauthorizing Ex-Im -- the most ever. This gave some inspiration to outside groups like the Club for Growth and Heritage Action, which have made Ex-Im a top issue this year.

The new chairman of Financial Services, Jeb Hensarling, was a traditional Ex-Im opponent. This year, he forcefully called for its abolition. Then this year, Dave Brat beat Eric Cantor -- a 2012 champion of Ex-Im -- by beating the free-market populist drum.

Suddenly, House Republicans see Ex-Im the way the grassroots do: a giveaway to large, politically connected corporations.

And Delta and the pilots' union have piped in. The airline is tired of the U.S. government subsidizing foreign airlines every time they buy a Boeing. For the first time, the subsidies have a corporate opponent. Delta's pilots and flight attendants are the biggest group at today's hearing. They want Ex-Im to stop subsidizing aircraft sales to credit-worthy private airlines and state-owned airlines.

If a vote were held today, Ex-Im would pass both chambers. Today's hearing on Ex-Im is Hensarling's first big step to try to persuade Republicans to listen to the grass roots and oppose corporate welfare.