The most important measure to watch in the campaign’s final weeks is how Democratic candidates are performing among voters who disapprove of President Donald Trump.

Many are not yet hitting the benchmarks among those voters they need to put away their races — especially in red-leaning states. But the challenge Trump’s decline presents to the GOP remains enormous. To avoid a wipeout in November, most Republican candidates this year will need to win significantly more voters who disapprove of Trump’s performance than almost any Republican did during his first term.

Since the 1990s, assessments of the president’s performance have become the most important factor in midterm elections. Averages that track presidential approval show that 60% or more disapprove of the job Trump is doing. That’s significantly worse than in the 2018 election, when exit polls found that 54% disapproved. His current position is also considerably weaker than Joe Biden in 2022, Barack Obama in 2010, George W. Bush in 2006 and Bill Clinton in 1994. That’s an ominous precedent for Republicans because those other presidents, and Trump himself in 2018, lost control of the House. Clinton, Bush and Obama also suffered major Senate losses.

During Trump’s first term, attitudes toward him shaped congressional elections even more powerfully than for his predecessors. Exit polls under Clinton, Bush and Obama found that 82%-86% of voters who disapproved of them voted for the other party’s House candidates. In 2018, the exit polls found, 90% of voters who disapproved of Trump supported Democrats for the House; in 2020, 93% of Trump disapprovers voted Democratic. Every Democratic Senate incumbent or challenger over those two elections likewise won at least 89% of voters who disapproved of Trump, except the Democrat who lost to Maine Republican Susan Collins in 2020.

Trump has a stronger down-ballot effect because he demands such complete loyalty that hardly any Republicans (apart, perhaps, from Collins and Alaska’s Lisa Murkowski) have established much of an independent identity. As important, though, is the intensity of opposition Trump provokes: The vast majority of voters who disapprove of him do so “strongly.” And voters who strongly disapprove of a president typically vote against his party’s candidates at much higher rates — often well above 90% — than the more ambivalent voters who “somewhat” disapprove.

At the same time, during Trump’s first term, Republican House and Senate candidates routinely won 90% or more of voters who approved of the president. These patterns meant few Democrats could win in places where Trump maintained majority approval — and even fewer Republicans triumphed in places where he did not. Dan Sena, who ran the Democratic Congressional Campaign Committee when Democrats recaptured the majority in 2018, says almost no House Republicans ultimately ran better than Trump’s approval rating in their districts.

If those dynamics repeat this November, the Democratic wave will reach towering heights. Public polling shows that most voters disapprove of Trump’s performance in every state where the two parties are most seriously contesting a Senate race; his disapproval rating has spiked to around 55% or more even in states he carried by double digits in 2024, including Ohio, Iowa, Alaska, and Texas.

So why, amid all this ominous polling for Trump, are Democrats not yet matching their first-term results among his disapprovers? Recent national New York Times/Siena College, Marquette Law School and NBC polls all found Democrats winning just 82-83% of Trump disapprovers in the House ballot — closer to the historic numbers for other presidents than the elevated levels seen in Trump 1.0. And recent Senate polls in North Carolina, Iowa, Ohio, New Hampshire and Michigan have likewise found Democrats winning only about 80% of voters who disapprove of Trump, with Troy Jackson in Maine attracting a meager 69% of them in last week’s NYT/Siena poll there. (Some other polls have shown Jackson doing better with them.)

One reason is that Trump-disapprovers now include more Republican-leaning voters, who remain resistant to voting for the other party despite their disappointment in the president. Democrats may also be lagging because their party’s image is weaker than in Trump’s first term.

Still, Republicans won’t find it easy to hold onto more Trump-disapprovers than during his first term; some recent Senate polls already show Democrats approaching their first-term numbers with his disapprovers in Georgia, Alaska and Texas. And because Trump’s disapproval is so high, Democrats can win in most places even without attracting as many disenchanted voters as in his first term.

“In every poll, in every race, the undecided…are conservative Trump critics at this point,” says Democratic strategist Pete Giangreco. “Some of them will hold their nose and vote Republican; some of them will hold their nose and vote Democrat. But I bet a big chunk of them just stay home.”

In the past few weeks, more Republican candidates have rushed to break from Trump on the Iran War, immigration enforcement, fuel prices, and tariffs. But even with these flickers of defiance, almost all Republicans have lashed themselves to Trump in his second term even more tightly than during his first. If Trump can’t recover over the next five weeks, the voters disillusioned with him will likely doom many of them too — no matter how hard they belatedly try to paddle from the wreckage.

Given how much attitudes toward the president now shape mid-term elections, defying history on a mass scale has become the GOP’s best chance in 2026.

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This column reflects the personal views of the author and does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

Ronald Brownstein is a Bloomberg Opinion columnist covering politics and policy. He is a CNN analyst and the author or editor of seven books.

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