Our most recent book is The Comeback: The 2024 Elections and American Politics. It includes a chapter on congressional and state elections. In 2024, the book explains, the Democrats' problems involved reality, not just messaging. Two years later, Republicans own the reality problems, including the Iran quagmire and the resulting economic pain. Tariffs make things even worse. Indeed, it is hard to think of any president who has indulged in such needless midterm self-sabotage.
You can infer what internal polls are telling candidates by looking at their ads. These numbers indicate that tariffs are really, really unpopular. From Greg Ip, WSJ:
President Trump once called “tariff” the most beautiful word in the dictionary. He has somehow made it one of the most hated words in politics.
In their midterm ads, Democrats repeatedly bash tariffs. Republicans, by contrast, are largely silent. One exception: Michigan Senate candidate Mike Rogers who calls to “end this tariff war now,” while gripping a Canadian-brand beer, now caught up in Trump’s trade war.
