President-elect Donald Trump is expected to nominate Robert E. Lighthizer as the U.S. trade representative, a transition official confirmed Monday night, recruiting to his Cabinet a veteran of the Reagan administration who has decades of experience in trade policy and litigation. Lighthizer, whose nomination is expected to be formally announced as early as Tuesday, will join a team of Trump lieutenants charged with fulfilling one the central promises of Trump’s populist candidacy: aggressively confronting China, Mexico and other nations the president-elect believes have been taking advantage of international trade agreements, to the detriment of U.S. workers.