Does a candidate need a job offer in order to immigrate to Canada under Express Entry?

Not necessarily, though the fact that Canadian employers play a greater role in Canadian immigration under Express Entry than they did previously means that, for many candidates, obtaining a valid job offer from a Canadian employer significantly increases their chances of being invited to apply for Canadian permanent residence. Candidates in the Express Entry pool have the opportunity to increase their chances of being invited to apply by promoting themselves directly to employers through the Canada Visa Job Search tool.