WASHINGTON — It’s nothing new for Pennsylvania’s two U.S. senators to split on a major initiative advanced by President Donald Trump.

But Thursday brought a twist.

Sen. Bob Casey, a Democrat, voted in favor of Trump’s much-hyped trade deal with Mexico and Canada (dubbed USMCA), while Sen. Pat Toomey was the only Republican to oppose it.

The measure passed, 89-10.

Toomey, who has put free trade and lower taxes at the center of his public career, has been an often lonely critic of the new agreement, which he argues will increase costs for U.S. consumers and businesses and increase uncertainty by imposing an expiration date on the new pact.

While most lawmakers in both parties supported the agreement, Toomey, on this issue, has railed against the plan for months in news conferences, Senate hearings, newspaper columns, and television appearances.

“For the first time in American history, we’re enacting a trade agreement that restricts free trade and reduces economic growth,” Toomey said in a statement. He said this deal would reduce trade between the U.S. and Mexico, and cited an analysis by the nonpartisan Congressional Budget Office that USMCA tariffs (“which are taxes”) would rise by $3 billion.

“This means higher prices — particularly on automobiles — for American consumers,” Toomey said. “Outside of a few necessary modernizations and modest market access improvements for Pennsylvania’s dairy farmers, USMCA is a step backwards and I could not support its passage.”

Casey, meanwhile, a critic of nearly all of Trump’s policies, has sided with him on trade, offering support for a deal that the president, and many Democrats, argue will shield U.S. workers from unfair foreign competition. The new pact alters the existing North America Free Trade Agreement, or NAFTA, which Trump has bashed as unfair to U.S. workers.

Even while backing one of Trump’s most highly touted initiatives, Casey singled out parts of the deal that were pushed by Democratic leaders, who urged changes to Trump’s initial agreement.

“The new NAFTA represents progress from the status quo,” Casey said in a statement. “The initial version negotiated by the Trump Administration was a corporate trade deal and completely unacceptable. Democrats in Congress made substantial improvements in enforcement and other areas, like allowing workers to bring cases against firms that violate their rights. It is only because of the Democratic improvements that I am able to support this agreement.”

The vote was a rare role reversal for Pennsylvania’s senators. Toomey has voted with Trump close to 90% of the time, while Casey has sided with the president on around 30% of Senate votes, according to an analysis by the data-focused website FiveThirtyEight.

Sen. Cory Booker (D., N.J.) voted against the deal, while Sens. Bob Menendez (D., N.J.), Tom Carper (D., Del.), and Chris Coons (D., Del.) supported it.

Most of the nine Democrats who opposed the deal did so over concerns that it failed to address climate change.

Republican leaders hailed the deal as a win for American businesses, arguing that it would expand vital export markets and boost the economy.

The House overwhelmingly voted in favor of the trade deal in December, with nearly every lawmaker from the Philadelphia region supporting it, except Rep. Donald Norcross (D., N.J.) of Camden County, a former labor leader. He was one of 41 “nay” votes against 385 votes in favor.

The Senate vote Thursday morning was the last major piece of legislation before the Senate begins the Trump impeachment trial. That debate is likely to see Toomey and Casey return to their familiar positions.