Republican defections would amount to rare public rebuke as concerns mount over impact of president’s plans

On the eve of Donald Trump’s so-called “Liberation Day” for tariffs, a handful of Senate Republicans are debating whether to defy the president and join Democrats to stop the US from imposing levies on Canadian imports.

The resolution, offered by the Democratic senator Tim Kaine of Virginia, would terminate the emergency order that Trump is using to justify tariffs against Canada, citing the flow of fentanyl across the US’s northern border. The vote is largely symbolic – the House is not expected to take up the measure – but several defections would amount to a rare and notable rebuke of the president by his own party.