Trump’s election-security czar last year sought to ban voting machines used in more than half of U.S. states by asking whether the Commerce Department could declare their components national security risks. White House adviser Kurt Olsen, who Trump was tasked with proving widely debunked election-rigging conspiracy theories, pushed the plan to target Dominion Voting Systems machines. The idea emerged, the sources said, as Olsen and other officials brainstormed about how the federal government could take control over elections from U.S. states, an idea publicly aired by Trump.