Republicans could be poised to deal a symbolic blow to President Donald Trump’s trade policy, with several GOP senators indicating they planned to join Democrats in a Tuesday vote to block blanket tariffs on Canada. Sen. Susan Collins (R-Maine) said Monday that she plans to back the resolution led by Sen. Tim Kaine (D-Va.) that would terminate the national emergency Trump declared last month, citing fentanyl trafficking and illegal immigration. Trump has used that declaration to justify 25 percent across-the-board tariffs on America’s northern neighbor and leading trade partner — duties that Trump has threatened to start levying later this...