Shares of Mastercard Inc. and Visa Inc. turned lower in Wednesday afternoon trading after The Wall Street Journal reported that two members of the U.S. Senate were working on a bill that would let merchants process Mastercard and Visa credit cards over unaffiliated networks. The report indicated that the bill could be debuted as early as this week and that it features bipartisan authorship, with Sen. Dick Durbin, an Illinois Democrat, and Sen. Roger Marshall, a Kansas Republican, looking to present the bill. Durbin is known for his efforts in the wake of the financial crisis to secure caps on debit-card interchange fees and create additional debit routing options, but credit-card fees remain a particular source of ire for merchants. The bill would aim to create more competition by making it so merchants wouldn’t necessarily have to steer transactions through the network whose brand is on the credit card a shopper uses. Visa shares had been trading in the black for most of the day in the wake of a better-than-expected earnings report but were off about 3% after the WSJ report came out. Mastercard’s stock followed a similar pattern as was recently off about 1%. Representatives from Visa and Mastercard didn’t immediately respond to MarketWatch’s request for comment.

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