House Financial Services Chairman Jeb Hensarling (R-Texas) questions Federal Reserve Chairman Ben Bernanke as he testifies on Capitol Hill in 2013. (AP Photo/Charles Dharapak)

When Jeb Hensarling assumed the helm of the House Financial Services Committee in 2013, the National Association of Manufacturers knew it had a problem.

The Texas Republican is the No. 1 enemy of the Export-Import Bank, whose charter a powerful faction of House Republicans is fighting to let expire on June 30. But NAM and its allies were never going to allow the feisty group led by Hensarling to win without a major battle — one that will only grow more intense over the next few weeks as Congress decides the credit agency’s fate.

NAM, which has long maintained its own in-house lobbying team, last year began adding more resources and manpower to its effort to save the bank while amping up lobbying spending to a nearly all-time high of $12.4 million in 2014 — a 63 percent jump compared to the previous year.

“We’ve put a massive amount of effort into the Ex-Im Bank since last year,” said Linda Dempsey, a veteran trade policy wonk and lobbyist at the manufacturers association. The group argues getting rid of the bank would hurt the thousands of manufacturing companies that rely on its loans to sell products overseas.

The lobbying fight to eliminate or save the obscure Ex-Im Bank is in now full swing and some of D.C.’s major players in the lobbying world have top billing.

Among the beneficiaries of NAM’s largesse are former House Majority Leader Dick Gephardt, a Democrat, and former Republican National Committee Chairman Haley Barbour, both the heads of top D.C. lobby firms, Gephardt Group and BGR Group, respectively. For their work on Ex-Im, Gephardt’s firm has earned $260,000 and Barbour’s firm has earned $350,000, according to lobbying records.

The Chamber of Commerce and NAM have also teamed up to create the coalition Exporters for Ex-Im, a group of 50 national, state and local business groups supporting the bank’s extension, in part to coordinate letter-writing campaigns to lawmakers and organize a fly-in. The coalition is represented by Hamilton Place Strategies, the advocacy firm run by former President George W. Bush aide Tony Fratto, whose efforts include tweeting at lawmakers to support the bank.

Weighing in for Boeing, which also wants to keep the bank in business, at various firms are Kyle Simmons, Senate Majority Leader Mitch McConnell’s former chief of staff; Sam Geduldig, former political director to John A. Boehner (R-Ohio) before he became Speaker; and John Scofield, a former top Republican House Appropriations Committee aide.

The Ex-Im bank was established in 1934 and for most of its history Congress has reauthorized its charter with little controversy. But in recent years it has sparked an intra-party battle between business-friendly Republicans, who argue it helps U.S. firms compete with foreign rivals, and their more free-market colleagues, who contend it’s a boondoggle for big manufacturers who don’t need taxpayer help.

The lobbying to kill the credit agency has been equally fierce.

Delta Airlines, the leading corporate voice opposing the bank’s reauthorization, has 17 lobbyists on retainer on the issue, spread across three firms: Elmendorf Ryan, Fierce Government Relations and Hoppe Strategies. Elmendorf Ryan earned $60,000 to lobby on Ex-Im and other issues for Delta during the first quarter of 2015. Fierce earned $80,000 during the same period. Hoppe was retained in February and has yet to report lobbying fees.

In some cases, retired lawmakers and their former aides who now earn their paychecks as lobbyists find themselves on opposite ends of the fight.

For instance, Democratic power broker Steve Elmendorf is squaring off with his old boss, Gephardt. And Republican lobbyist Kirk Blalock, of Fierce Government Relations, is going up against Barbour, for whom he worked at the RNC.

And the messaging strategy on both sides goes beyond traditional lobbying, bringing in paid advertising, grassroots advocacy and social media outreach.

Delta, which objects to the bank helping competing foreign carriers like Emirates’s buy Boeing jets, has deployed its pilots, flight attendants and other employees to bring their concerns to lawmakers. The airline has estimated that the bank has cost the U.S. airline industry up to 7,500 jobs and $684 million a year.

“Delta’s employees have been leading that effort,” a company spokeswoman said in a statement. “Pilots, flight attendants, customer service agents, ground employees and many others have made hundreds of visits with members of Congress over the past several years.”

The airline does not coordinate with the conservative groups that also want the bank put out of business, but for ideological not competitive reasons.

The Club for Growth, the Koch-backed Freedom Partners and Heritage Action, the advocacy arm of the Heritage Foundation, oppose the agency because they argue it is corporate welfare that distorts the marketplace, and point out that the biggest recipients of Ex-Im financing include Boeing, General Electric and Caterpillar.

Those groups have not hired formal outside lobbyists, but are spending money in other ways: The Club for Growth this spring launched a $1 million advertising campaign against the bank, including a $250,000 TV ad in Florida that calls the agency “outrageous corporate giveaway.”

The ad campaign, which urges Republican members to vote against Ex-Im reauthorization, began in April targeting Reps. Stephen Lee Fincher (R-Tenn.), Earl L. “Buddy” Carter (R-Ga.), Renee L. Ellmers (R-N.C.) and Bill Flores (R-Tex.). In May the Club announced it would expand the campaign to focus on Reps. Rob Bishop (R-Utah), Bill Shuster (R-Pa.), David B. McKinley (R-W.Va.) and Chris Stewart (R-Utah), though it later said it would not air the ads on Bishop and Stewart after both declared their opposition to reauthorization.

Heritage Action, the advocacy arm of the Heritage Foundation, has only 10 paid staffers but is banking on its network of 10,000 “sentinels” — a mix of Tea Party elected officials, Republican activists and other conservatives — to get the word out. Heritage Action’s vice president of grassroots outreach Russ Vought, a former Hensarling aide, holds phone calls every Monday night with the network to brief them on updates.

“We have these folks in every congressional district across the country,” said Dan Holler, communications director for Heritage Action. “It’s a pretty wide reach. Our volunteer network, they text back and forth with members, or have a direct line of contact to a chief of staff in D.C.”

Holler said the grassroots model pre-dates the Ex-Im fight and it is now being put to good use.

“We’ve been doing pretty much the same things we’ve been doing since 2012 but with more urgency, given the deadline,” Holler said.

Clarification: This post has been updated to note that the Club for Growth decided not to air the ads in Bishop and Stewart’s districts after both announced they opposed extending the bank’s charter.