A credit-card bill that could dent banks' profits and erode Visa's and Mastercard's dominance has a new champion, and he sits in the Oval Office.

President Trump, Vice President JD Vance and some top lieutenants on the campaign trail have endorsed a long-stalled legislation that would give merchants the option to choose a different card network to process transactions when their customers use a credit card.

The legislation has the potential to upend the system of billions of dollars in fees that drive the credit-card industry, which means the president's support has merchants salivating and some bankers concerned.

Large merchants have advocated for the bill for years, arguing it would lower the fees they pay when customers use a card and allow them to pass the savings onto consumers. Banks say that the fees are what power credit-card rewards, like cash back and travel points, and that passing the bill would force them to change those programs consumers love.

The Credit Card Competition Act was originally introduced in 2022 with bipartisan support from Sens. Dick Durbin (D., Ill.) and Roger Marshall (R., Kan.). When he was a senator, Vance added his name as a co-sponsor. Trump and others have picked it up as part of efforts to talk about affordability issues with the public.

The bill aims to add competition to the card networks that connect the consumer's bank to the merchant's and move the payments, an industry dominated by Visa and Mastercard.

Currently, a card issuer (like a bank) partners with a network for each card, determining the rails that will be used to move the payments. The network determines the fees that are charged each time a card is used, but the money is mostly pocketed by the issuer.

Under the bill, each card issued by a major bank would be required to support at least two networks, including smaller competitors, allowing merchants to choose a network that charges a lower fee.

These swipe fees, known as interchange, are the center of long-running fights between merchants and card companies.

A lawsuit between merchants and card companies raged for more than 20 years until it reached a settlement last year that is already set to make some changes. The settlement would reduce fees and allow merchants to break a cardinal rule the card companies had long insisted on: accepting all cards on a network.

While it bent there, the payments industry says the competition bill would lead to more changes that would ultimately harm consumers. The industry dismisses the bill as unlikely to pass in any form and views Trump's support as campaign rhetoric.

Merchant lobbyists have had conversations with White House officials in recent weeks about a route to passing the bill, according to people familiar with the matter. They are seeking to tack the bill onto an existing piece of legislation after the midterms but before Congress turns over.

Banks and payment lobbyists have launched into action. Since Trump's initial post on social media promoting the legislation in January, executives and trade groups have had a steady drumbeat of meetings with administration officials and members of Congress.

The industries on both sides have spent tens of millions lobbying the bill since its introduction several years ago.

"President Trump has been clear: Pass the Credit Card Competition Act and save American families from hidden swipe fees that cost households $1,200 a year," Taylor Rogers, a White House spokeswoman said. "He continues to urge Congress to meet this moment, put Main Street over Wall Street, and get this legislation to his desk."

The bill's co-sponsor and one of its most dedicated advocates, Republican Sen. Roger Marshall, faces a tight re-election race in Kansas, and Trump has praised Marshall's support for the bill in a campaign endorsement.

"He also been a champion of a bill we're going to pass as soon as possible -- it's going to happen quickly -- to eliminate out-of-control credit-card swipe fees," Trump said in a video promoting Marshall. "It's a big deal."

For big banks, the Trump administration has been a mixed bag. Regulators have ushered in looser regulation for financial institutions and a more permissive dealmaking environment, while buoyant stocks and more initial public offerings have propelled banks to record profits.

Meanwhile, Trump has targeted the banks for so-called debanking, or improperly closing customer accounts for political reasons, with executive orders and official investigations.

His focus on credit cards has particularly vexed the bankers. In January, he said he wanted to temporarily cap credit-card interest rates at 10%, alarming CEOs.

Many on the banking side still see the Credit Card Competition Act as having little to no chance of passing or of being added to another piece of legislation -- but even a small chance of success necessitates a code red.

Banks and networks have seen this movie before. Debit-card fees have been capped since 2011 under an amendment added to the landmark Dodd-Frank Act, despite heated opposition from those parties. Financial institutions and their lobbyists have long lamented that the amendment didn't go through typical Senate committee channels, instead getting tacked on in a last-minute addition by Sen. Dick Durbin.

Banks say the Durbin amendment is evidence that this bill won't work: They argue that the cap on debit-card fees didn't effectively lower any consumer prices.