Three weeks after it looked like Donald Trump could challenge Hillary Clinton in Michigan, it now appears the Republican nominee may have squandered that chance with a poor debate performance, revelations about his taxes and erratic behavior on the campaign trail, an exclusive new Free Press/WXYZ-TV poll shows.

The poll showed Clinton, the Democratic nominee and former secretary of state, regaining an 11-percentage-point lead over Trump, 43%-32%, and clawing back levels of support among key voting blocs including women, African Americans and millennials. It came less than a month after a more-disciplined Trump had closed the gap to 3 percentage points in Michigan, which hasn’t voted for a Republican presidential nominee since 1988.

Now, with less than five weeks until the Nov. 8 election, Trump, a businessman, real estate mogul and reality TV star, may have a tough time trying to take back the momentum in a key battleground state; with his already high negative ratings climbing even higher and segments of the public he was counting on to win — men and voters with a high school diploma or less education — not backing him as strongly as was expected, at least not for now.

A poll taken Sept. 10-13 had Clinton leading 38%-35%.

“The race is much more settled now no matter what demographic group you’re looking at,” said Bernie Porn, the pollster for Lansing-based EPIC-MRA, which performed the survey for the Free Press, WXYZ-TV (Channel 7) and their outstate partners. “It’s hard to imagine (Clinton losing Michigan) unless Hillary has a health (or some other) issue … I think the perceptions of Trump are pretty baked in.”

Trump could potentially close the gap with a strong second debate performance Sunday at Washington University in St. Louis. But he'd almost certainly need other help in the form of a Clinton stumble — such as when she called a portion of Trump's supporters "deplorables," a remark she later retracted — or new revelations about her time as secretary of state or continued scrutiny of her husband's charitable foundation.

But that would also require Trump to show far more discipline and stay on message in the face of continuing revelations and questions regarding his own foundation and its structure, his past behavior and business dealings, and a level of experience and temperament that have led many leading conservative-leaning publications to withhold their endorsements from him in recent weeks.

The Michigan poll — for which 600 likely voters were surveyed from Saturday through Monday and which has a margin of error of plus or minus 4 percentage points — showed Clinton staking out the same 11-percentage-point lead over Trump she had following her party’s nomination convention in Philadelphia in July. More troubling for Trump, it continues a recent string of poll results that show him losing ground nationally and in battleground states including Florida, Colorado, North Carolina, Pennsylvania and others.

In a two-person race, the poll showed Clinton with a 10-percentage-point — 46%-36% — lead over Trump.

Asked about all four major candidates running, 43% of those surveyed backed Clinton, with 32% for Trump, 10% for Libertarian Gary Johnson, 3% for the Green Party’s Jill Stein and 12% undecided. In September, Trump had cut Clinton's lead in Michigan to 38%-35%.

That poll and others like it that showed Trump closing the gap on Clinton nationally and in battleground states increased the likelihood that he could catch Clinton, who still has the edge. Since then, however, it has been mostly bad news for Trump's campaign.

Much of Trump’s recent problems can be traced to his uneven performance in the first presidential debate Sept. 26, which most viewers nationally and 61% of those surveyed in the Free Press poll believed Clinton won, hitting him repeatedly on questions of temperament and judgment in a format far from the more freewheeling affairs he occasionally dominated during the Republican primary season.

Voters say that Hillary Clinton won the debate over Donald Trump.

But even after that, Trump had a series of setbacks: pursuing an ongoing feud with a former Miss Universe he was accused of having criticized for gaining weight; a middle-of-the-night series of tweets blasting journalists and others that raised questions about his judgment; and a report in the New York Times that indicated Trump, who has not released his federal income taxes unlike most other recent nominees, potentially may not have paid any for more than a decade because of a business loss of more than $900 million in the 1990s.

Abandoning what had been seen as a more disciplined attitude on the campaign trail, Trump also seemed to mock Clinton for stumbling when she was sick with pneumonia a few weeks ago and suggested that the Democratic nominee may not be “loyal” to her husband, former President Bill Clinton. Trump had already said he might touch on accusations and instances of infidelity involving Bill Clinton — and his wife’s responses to those — in future debates, including the one set for 9 p.m. Sunday.

In three weeks since the last EPIC-MRA poll, Trump’s unfavorable ratings rose from 63% to 66% while Clinton’s own number fell from 56% to 52%, an indication many voters may be softening their criticism of her. It also doesn’t hurt that her surrogates — President Barack Obama, first lady Michelle Obama, U.S. Sen. Bernie Sanders of Vermont and even Bill Clinton — all have favorability ratings of 50% or higher.

The poll, meanwhile, showed clear momentum for Clinton heading into the home stretch among increasingly important demographic groups in Michigan.

For instance, a month ago, as questions about her health dogged her as she went off the campaign trail briefly due to a bout of pneumonia, Clinton’s support among black voters in Michigan dropped to 74% — far below the 95% of support Obama got in the last election — and 14% undecided. This poll, however, showed 86% of black voters supporting her and Trump getting no more than 2% of that vote despite his outreach in visits to Detroit and Flint to dig into that support. Only 5% of African-American voters remained undecided, the poll said.

Trump’s chances of winning in Michigan and elsewhere despite that are further hurt by an inability to attract more support from whites as well: The poll indicated that Clinton was leading among whites 41%-32% in Michigan, compared to 10% for Johnson and 12% undecided. In the last election, exit polls showed Republican nominee Mitt Romney beating Obama among whites in Michigan by 11 percentage points — and still losing by 9 percentage points overall in the state.

Three weeks ago, Trump also had taken a clear step toward neutralizing the gender gap facing his campaign, taking a 5-percentage-point lead among men and cutting Clinton’s clear lead among women to 10 percentage points.

In this poll, however — following Clinton’s debate where she said Trump had called 1996 Miss Universe Alicia Machado “Miss Piggy” and “Miss Housekeeping” when he owned the pageant — Clinton had staked a 20-percentage-point margin — 48%-28% among the biggest single voting bloc in the state. She has continued to raise issues of Trump shaming women over their looks or their weight on the campaign trail.

Meanwhile, where Clinton had seen a decline in support among younger voters — those 18 to 34 — in the last Michigan poll, she’s now back where she was with them post-convention, with a 44%-22% lead over Trump and Johnson getting 21%. Clinton also held leads among every other age demographic. And in vote-rich metro Detroit, Clinton’s support was back over 50%: She led Trump in Wayne, Oakland and Macomb counties as a bloc by 55%-25%, though Trump still leads in central, west and northern Michigan.

Trump had been expected to do best with voters with a high school diploma or less education, but after holding a 4-percentage-point edge with those voters last month, Clinton regained a clear lead, 41%-32%. She also reclaimed a lead among self-described independent voters, 27%-24%, though what may be most significant about that group is that their number of undecideds jumped from 20% to 31%; and their support for Johnson dropped, from 23% to 14%, as the third-party nominee had difficulties identifying the war-torn city of Aleppo in Syria and answering a question about foreign leaders.

With 34 days until the election, there is little good news in the poll for Trump. While slightly more than half of those surveyed rated their enthusiasm about voting as high (7 or above on a scale of 1 to 10), Clinton enjoyed the greater support by far of most of those voters. And while voters who considered international trade deals and national security their top issues tended to favor Trump over Clinton, they made up far fewer voters than those caring most about jobs and the economy, improving education and wages — and she did far better than he did with those voters.

Still, if past is prologue, Trump could continue to make a strong play for Michigan: Since the end of the nominating conventions in July, he has made five trips to the state — far more than other recent Republican nominees — though neither he nor Clinton have spent much money (or in Clinton’s case, any money) on TV ads in Michigan. If he can’t mount another comeback in Michigan or other Rust Belt states — Pennsylvania or Wisconsin, for instance — it could make his path to the White House impossible.

Porn, of EPIC-MRA, said all of the evidence from recent polls across the country seems to suggest the race is moving in one direction, however — and it’s not a favorable one for Trump.

“Given that his unfavorables have gone up, it can’t just be the debate. It has to be his overall behavior,” Porn said. “All of these things are turning people off. … It’s significant and it’s consistent to what we’re seeing in other states.”