President Donald Trump announced today that the United States and Mexico agreed in concept to overhaul portions of the North American Free Trade Agreement, but Congress won’t be able to ratify the deal until next year – under what could be Democrat majorities on Capitol Hill if November’s elections go poorly for Trump.

Trump made the announcement from the Oval Office with Mexican President Enrique Peña Nieto on speakerphone. Trump said he was “terminating” NAFTA and entering into what he called the “U.S.-Mexico Trade Agreement.”

Details of the agreement haven’t been announced, but some specific changes – like on automobiles – were being released by the administration.

Canada is not part of the new agreement, and Trump replied with a frosty “we’ll see” whether Ottawa would join the deal. The president hinted at rough negotiations ahead for Canadian Prime Minister Justin Trudeau when he said “the easiest thing we can do” is put tariffs on vehicles assembled in Canada and imported into the United States.

U.S. Trade Representative Robert Lighthizer said the Trump administration will notify Congress on Friday that it intends to sign a trade deal with Mexico before the end of November. It may take six months or longer for U.S. lawmakers to review and approve a renegotiated NAFTA, even if it’s only with Mexico.

Under the 2015 Trade Promotion Authority law that establishes how trade deals are enacted in the United States, the White House must notify congressional leaders of its intent to sign a trade agreement within 90 days. At least 60 days before any deal is signed, the full text of the agreement must be made available to Congress.

Only simple majorities in the House and Senate are required to enact trade agreements. No amendments are permitted; it’s a straight up-or-down vote.

But before lawmakers cast their votes, numerous congressional committees are likely to hold hearings to examine the agreement. Some Republican-run committees may want to examine the emerging agreement as soon as next month.

It’s not clear whether Republicans will maintain their congressional majorities after the November midterm elections. Traditionally, Democrats and their political allies in organized labor have opposed trade agreements, particularly NAFTA. It’s not immediately known if the new agreement with Mexico would win over Democrats’ support.

If Democrats do win control of the House, they are expected to confront Trump aggressively in 2019 with oversight investigations and policy rejoinders. Some Democrats even want to begin impeachment proceedings against Trump immediately.

In that toxic and highly charged partisan environment, it’s not clear whether Democrats would push to ratify a U.S.-Mexico trade agreement negotiated by Trump. But at least when it comes to trade, Trump has always sounded more like a Democrat than a Republican over the decades. Endorsing a new trade agreement with Mexico could be one issue Trump and a Democrat majority in the House could agree on.