Ted Cruz, a Republican senator who has been a staunch supporter of Mr. Trump, warned of the administration's move to back up the ante tariffs, saying they would pose a "huge risk" to the US economy and could leave Republicans facing a "crushing defeat" in next year's midterm elections. In a podcast released on Friday, Mr. Cruz said long-term trade tariffs would drive up inflation and hit markets hard, with the economic consequences likely to help Democrats retake the House of Representatives and possibly even win a majority in the Senate, albeit with a small probability.