As Americans casted their final votes Tuesday, former prime minister Brian Mulroney reminded Canadians that the country has “a lot at stake” and warned that a Joe Biden presidency could be just as protectionist as the current Trump administration.

Mulroney, who played a key role laying the groundwork for the original NAFTA, said strong ties between Biden’s Democratic Party and unions that are traditionally protectionist could pose challenges for the former U.S. vice president to stay committed to free trade with Canada if he wins the election.

“[The Democrats] are essentially liberal traders,” Mulroney told BNN Bloomberg’s Amanda Lang in an interview. “But they’ve got the constraints of protectionists within their own party. Of course, the ‘America First’ policies of President Trump are concerning to the same extent.”

Mulroney’s comments come the same day Americans headed to polling stations across the country, with national surveys and polls of most key U.S. states giving Biden a lead over Trump.

Biden has been widely perceived as more liberal when it comes to trade than Trump, who has engaged in trade wars and imposed several protectionist policies, including tariffs on some Canadian goods and the renegotiation of NAFTA.

Mulroney says trade remains the key issue for Canadians in this election and that the country should pursue a good relationship with the next U.S. administration, no matter the winner.

“[Canada-U.S. trade] is the object of this exercise – apart from having good relationships on other areas with our neighbours simply because we can’t do without them,” Mulroney said.

“We have a lot at stake tonight.”