Both exit polls in 2017 and analysis of recent generic congressional ballot polls — which indicate a Democratic lead — show that willingness to vote Republican or Democratic is highly correlated with one’s opinion of President Trump. That can mean only one of two things: Either people who voted for Mr. Trump without liking him are so discouraged they aren’t even answering polls (unlikely) or millions of Trump voters are intending to vote for Democrats in the fall.

That probably shocks political pros from both sides of the aisle. Mr. Trump’s first year in office, while tumultuous, followed a predictable script. He signed the Republicans’ signature agenda item, a giant tax-cut bill. He pursued a traditional business-friendly Republican program for deregulation and promoted conservative priorities like stricter immigration policy. He appointed the conservative judge Neil Gorsuch to the Supreme Court, regularly attacked the news media and provoked liberals with culture-war tweets (like berating N.F.L. players for kneeling during the national anthem).

This combination of stoking racial resentment and promoting Republican policy was supposed to be his ticket to victory. Yet his job-approval ratings continued to fall during the year, hitting a nadir about the time he endorsed Roy Moore, who lost in Alabama’s special Senate election.

It’s not a surprise, though, if you look at the characteristics and beliefs of these “reluctant Trump” voters. According to the George Washington University Battleground Polls from September and October 2016, which also tracked voters who disliked both candidates, these people were largely self-described independents and ticket splitters. They leaned Republican, but they were not hardened partisans. Instead, they were willing to break with their preferred party when personalities or circumstances permitted.

These polls also make crystal clear how much Mr. Trump bothered them. In both sets of the battleground polls, these voters strongly thought Republicans were best able to handle taxes, jobs, the economy and foreign affairs. Yet when they were asked the identical questions about which of the two candidates they trusted more, they backed Mrs. Clinton or rated the two evenly. They also strongly thought Mr. Trump did not have the temperament for the job, nor was he honest and trustworthy.