Two days before their final televised faceoff, President Trump on Tuesday attacked the upcoming debate as yet another campaign event that would be “a stacked deck” against him, while Joe Biden’s camp hunkered down and strategized over Trump’s expected attacks on his family.

The maneuvering came as both sides prepared for the last scheduled event that could change the trajectory of the campaign and wrestled with what it would mean that the debate will feature a mute button for the first time. Biden held no public appearances for a second straight day, while Trump tried out lines of attack and in essence held his debate prep in public.

In a phone interview broadcast on “Fox & Friends,” Trump lashed out at the moderator of Thursday’s event, NBC’s Kristen Welker, as “totally partisan” and sought to portray the debate topics and rules as unfair.

“There are people out there that can be neutral. Kristen Welker cannot be neutral,” Trump said, adding that she comes from a Democratic family. An official from the Commission on Presidential Debates defended Welker, noting that a Trump official had praised her just last week, and said both campaigns had agreed to the rules. The president has complained about previous moderators as well.

The debate, set to take place in Nashville just 12 days before Election Day, is the clearest opportunity for Trump to shift the dynamic of a presidential race whose contours have remained stable despite numerous surprises. Biden leads Trump by 11 percentage points nationally, 54 percent to 43 percent, according to an average of national polls since Oct. 4.

It could also take on added significance because the previous matchups were so chaotic. The first debate was dominated by Trump’s interruptions and determination to talk over Biden, and the second faceoff was canceled after Trump contracted the coronavirus, resulting in separate, dueling town halls.

At the first debate, Trump’s entourage ignored rules that they had to wear masks, but organizers have signaled that they will not permit such behavior this time.

The Commission on Presidential Debates decided unanimously this week to mute each candidate’s microphone during the opening two minutes of his opponent’s remarks on each of the six featured topics. The debate sponsors said the change was a way to enforce rules that the campaigns had already accepted.

Commission Co-Chairman Frank J. Fahrenkopf Jr. said in a recent interview that the debates had to be changed “for the American people to have a better experience” after the unruly first faceoff. He said Trump’s team had agreed to the rules before that first debate, and he noted that the candidates could go back and forth for the remaining 11 minutes of each segment.

Fahrenkopf also said the Trump campaign’s assertion that this debate was initially supposed to be about foreign policy was “entirely false.”

Some Trump advisers were annoyed with the change but kept their protests to a minimum because they believed that the president’s interruptions in the first debate hurt him, three advisers said.

With two weeks before the election, Biden is keeping an unusually light public schedule. In the past four days, he has traveled outside his home state of Delaware just once, to North Carolina on Sunday. On Monday, he taped an interview with “60 Minutes,” which will air over the weekend, but held no public events.

Biden’s surrogates have kept a robust travel schedule in his place: Sen. Kamala D. Harris (D-Calif.), his running mate, campaigned in Florida on Monday, and former president Barack Obama is scheduled to hold his first public event for Biden in Philadelphia on Wednesday.

In any other presidential race, such a low-key approach would be extremely unusual at this juncture. In the midst of the coronavirus pandemic, however, it has become emblematic of Biden’s campaign. The former vice president has blasted Trump for holding large in-person rallies, calling them “superspreader” events, and has hewed to smaller, socially distanced gatherings or drive-in car rallies while on the trail.

Trump, meanwhile, has taunted Biden for his sparser public schedule and has continued crisscrossing the country in the past week, holding rallies from Arizona to Pennsylvania as he seeks to make up ground during the final stretch.

Trump has not undertaken the same kind of formal preparation as before the first debate, when he was peppered with questions by former New Jersey governor Chris Christie, former New York mayor Rudolph W. Giuliani and others. Instead, he has taken some informal questions from advisers such as Jared Kushner and Hope Hicks.

Trump allies including Christie and former presidential counselor Kellyanne Conway have encouraged the president to change his strategy and let his rival speak more. “My main advice is to let Biden speak. After 60 or 70 minutes, he’ll be worn out,” Conway said.

Trump hinted Tuesday that he may oblige. “Actually, the interesting thing, they said if you let him talk, he’ll lose his train of thought,” Trump said of Biden on Fox. “There were a lot of people that say let him talk because he loses his train.”

Trump’s advisers have made it clear they are unhappy with the selected topics for the debate, arguing that foreign policy should play a more central role and that Biden should be forced to address alleged emails from his son Hunter that were recently published in the New York Post.

The Trump team argued that foreign policy is traditionally the focus of the final presidential debate, but Fahrenkopf said that has not been true for years. National security is one of the listed debate topics, along with fighting the coronavirus, American families, race in America, climate change and leadership.

Trump wants and plans to bring up Hunter Biden during the debate, though some of his advisers would prefer that he focus on the economy and Joe Biden’s record, aides said, painting the former vice president as a liberal who would raise taxes. Trump charged Tuesday that Biden would turn the United States into a “socialist hellhole.”

Biden’s advisers, for their part, see little to be gained by engaging publicly in the details of Hunter Biden’s alleged emails and texts beyond what they have already said, according to people with knowledge of their thinking. These people, who spoke on the condition of anonymity to more candidly describe strategy, said there is no reason to give credibility to a report that is sourced in part to close allies of Trump and has prompted considerable public skepticism. The Washington Post has not independently verified the contents of the report.

But ignoring the matter altogether is not an option either, they said, leaving some uncertainty about how Biden will address it Thursday night.

“I know how I would react, which would be very angry,” said Sen. Robert P. Casey Jr. (D-Pa.), a Biden ally, stressing that he was not speaking for the campaign. “The whole thing is just another pack of lies in a desperate, last-minute smear campaign.”

Biden did show a flash of anger when he was asked about the subject last week. “I have no response. It’s another smear campaign, right up your alley,” he told a CBS News correspondent who asked about the New York Post’s reporting.

The tensions surrounding the issue were evident Tuesday. Biden spokesman Andrew Bates sent a preemptive warning shot at Trump, who has appeared eager to bring up Biden’s son. “He invests in these tainted smears,” Bates said, “because he knows his presidency is a weak, pathetic failure.”

Substance aside, Biden should show that he can stand up to Trump in the debate, said former Pennsylvania governor Ed Rendell, a longtime Biden ally who has been raising money for his campaign.

“He should push back a little bit — not a lot, a little bit — so he doesn’t look weak,” Rendell said. “They’ve been peddling this thing that he’s too weak to be president. . . . He’s got to smack back.”

Questions also remain about how the debates commission will enforce public health guidelines inside the hall this time.

Trump — as well as several people involved in preparing him for the first debate — contracted the coronavirus after that event, and the unmasked prep sessions were among the suspected sources of the virus’s spread.

Trump has refused to disclose the date of his last negative test before he contracted the virus. After Trump was hospitalized with covid-19, the Commission on Presidential Debates decided that the second debate would be virtual, prompting the president to angrily withdraw.

Biden has repeatedly said he would follow whatever guidelines the commission issues.

“Look, I’m going to abide by what the CPD rules call for,” Biden said during his town hall when asked whether he would demand that Trump test negative.

Biden also said he was “confident” that the Cleveland Clinic, which is overseeing the public health practices of the debates, would ensure adherence to its guidelines.

Toluse Olorunnipa, Michael Scherer and Annie Linskey contributed to this report.