American voters have handed control of Congress to the Democrats in a sweeping midterm-election defeat for President Donald Trump’s Republican Party—a political shift that could also have consequences for Canada.

Democrats secured majorities in both the House of Representatives and Senate, giving the party control of Congress during the final two years of Trump’s presidency.

The party gained more than two dozen House seats and flipped at least seven Senate seats, including traditionally Republican seats in Texas, Iowa, Kansas and South Carolina.

Voter concerns about the cost of living, the war in Iran and allegations of government corruption contributed to the result.

Democratic control of Congress will allow the party to block much of Trump’s legislative agenda, reject presidential nominees and launch investigations into his administration.

The change could also bring increased congressional scrutiny of American tariffs on Canadian steel, automobiles and other products.

The trade dispute became an election issue in several border states where businesses and workers depend heavily on commerce with Canada.

However, the change in congressional control will not automatically eliminate the tariffs. The American president retains considerable authority over trade policy, and Trump could veto legislation passed by the Democratic-controlled Congress.

The new majorities will still provide Democrats with greater power to hold hearings, apply political pressure and influence future negotiations between Washington and Ottawa.

Prime Minister Mark Carney’s government has been holding discussions with the Trump administration, although Canadian officials recently reported only limited progress toward an agreement.

Several individual races remain undecided, meaning the final size of the Democratic majorities in both chambers is not known at the time of this writing.