TORONTO—A campaign pledge by Canada’s ruling Liberals to raise corporate taxes on banks to help pay for pandemic relief could lead to job cuts and higher borrowing costs as the lenders take steps to protect their profits, investors and political analysts said. Seeking an edge in a tight race ahead of the Sept. 20 election, Prime Minister Justin Trudeau said last month his party, if re-elected, would hike the net tax rate on the country’s most profitable banks and insurance companies to 18 percent from 15 percent on all earnings over C$1 billion ($792 million), generating C$2.5 billion a year over four years. Trudeau said that given the banks’ big profits, “we’re going to ask them to do a little bit more” to help deal with the country’s recovery from the pandemic. His government has run up record deficits dealing with COVID-19, drawing fire from the main opposition Conservatives, who …