Republican presidential nominee Donald Trump seemed to be gathering steam last month, closing the gap with Democratic nominee Hillary Clinton in most national polls and even pulling ahead in some key swing states.

But what a difference a few weeks can make.

Trump’s bid been rocked by a number of controversies and setbacks of late: A poor first debate performance, a revelation that he could have avoided paying federal income taxes for 18 years, and the now-infamous 2005 tape of Trump bragging that his celebrity allowed him to grope women with impunity, among other developments.

It has all taken quite a toll: according to a raft of new survey data released this week, Clinton again holds a significant lead nationally and in most battleground states. With just 26 days to go before Election Day - and with early voting already underway in a number of swing states - Trump’s window to shift the momentum in his favor is closing rapidly.

New national polls

After watching herself fall to within one point of Trump in the RealClearPolitics average of national polls in mid-September, Clinton is again out in front, holding a 6.2 percent lead in an average of head-to-head polls.

A Reuters/Ipsos poll released Wednesday found Clinton with a seven-point lead, 44 to 37 percent, in a two-way race. (She held an identical lead in the four-way matchup, including Libertarian nominee Gary Johnson and Green Party nominee Jill Stein, according to Reuters.)

An Atlantic/PRRI poll released Tuesday found Clinton ahead by 11 points, 49 to 38 percent, among likely voters nationwide in a two-way race. Some NBC News/Wall Street Journal numbers also released Tuesday found a similar state of play – Clinton ahead by nine points in a four-way race, and ahead by 10 points in a two-way race.

And in an NBC News/SurveyMonkey poll released Monday, Clinton held a bit of a slimmer lead: seven points in a head-to-head race, and five points in a four-way race.

New state polls

Clinton’s growing lead in national polls has also been reflected in statewide surveys, which show Clinton ahead in most of the states that will determine the outcome of the election.

Our latest CBS News Battleground Tracker numbers, released Sunday, showed Clinton ahead in three key Midwestern states: Ohio, Pennsylvania, and Wisconsin. In Ohio, where a number of surveys showed Trump leading throughout September, Clinton now holds a four point edge, 46 to 42 percent.

In Pennsylvania, according to the CBS News Battleground Tracker, Clinton is ahead by eight points, 49 to 41 percent. Similarly, a Bloomberg poll released Thursday found Clinton ahead by nine points in Pennsylvania, 48 to 39 percent. And a Susquehanna poll released Tuesday found Clinton ahead by four points, 44 to 40 percent, in the Keystone State.

In Wisconsin, according to our latest survey, she also holds a four-point lead, 43 to 39 percent. That lead is fairly consistent with Clinton’s lead in other recent Wisconsin surveys: a Marquette University poll released Wednesday, for example, found Clinton ahead by seven points in a four-way race, and by four points in a two-way race.

The Marquette poll demonstrates the damage one of Trump’s recent scandals inflicted on his polling numbers. The survey was in the field from October 6 through October 9. On October 7, the 2005 video of Trump bragging about groping women was released. Responses collected the day before the tape went public showed a competitive race, with Trump actually leading 41 to 40 percent. But then the tide began to turn. On October 7, respondents supported Clinton over Trump 44 to 38 percent. And by October 8 and 9, her lead had expanded dramatically: voters who responded to the survey on those days preferred Clinton by a 49 to 31 percent margin. The results suggest that Trump’s position in Wisconsin could actually be worse than the Marquette poll reflects, given the dramatic erosion in his support during the poll’s surveying window.

Clinton also leads in another rust belt battleground state, Michigan, according to a poll released Wednesday by the Detroit News. In the four-way race, she was up by 11 points, 42 to 31 percent. And in a head-to-head race, her lead expanded to 14 points – 47 to 33 percent.

Early voting

With early voting already underway in a number of key battleground states, polls taken today don’t just represent a snapshot that could change by Election Day. They reflect an electorate that, in some cases, is already rendering a decision - and if that decision is tilting against Trump, it could make his uphill climb to victory on November 8 even steeper.

According to returns analyzed by CNN, before the tape of Trump’s lewd remarks about women surfaced last week, more than 450,000 ballots had already been cast in the 2016 presidential race. In nine battleground states - Virginia, Wisconsin, Colorado, Iowa, Florida, Michigan, Ohio, North Carolina, and Nevada - approximately 190,000 early votes have been cast.

Early voting patterns in some states seem to favor Clinton, according to a New York Times report this week. “Democrats are requesting more absentee ballots in Florida than they were at this point in 2012, with increases of 50 percent in the heavily Hispanic areas around Miami and Orlando,” the report found. “In North Carolina, where Mitt Romney built enough of a lead in early voting four years ago to eke out a victory over President Obama, Democrats are requesting mail-in ballots in larger numbers than in 2012, while Republicans’ participation is declining.”

Clinton’s campaign manager, Robby Mook, told the New York Times that vote-by-mail requests among Hispanic voters, who have heavily favored Clinton, are up 77 percent compared to last cycle. And according to University of Florida political science professor Daniel Smith, only 16 percent of Latinos who have registered to vote since January 1 have registered as Republicans. In 2012, 28 percent of new Latino registrants identified with the GOP.