Doug Jones, left, and Roy Moore (AP; Bloomberg)

National political leaders, a Hollywood actress and a retired basketball star made last-ditch efforts Monday to woo voters in Alabama's U.S. Senate race, as the candidates gave their final arguments in a pivotal special election that has attracted more than $41 million in spending.

Former president Barack Obama and former vice president Joe Biden recorded robo-calls for Democrat Doug Jones, while President Trump recorded an appeal for Republican Roy Moore.

“If Alabama elects liberal Democrat Doug Jones, all of our progress will be stopped cold,” Trump said in his recorded message.

For his last event of the campaign, Moore brought in a raft of out-of-state conservative activists, including former White House adviser Stephen K. Bannon, Rep. Louie Gohmert (R-Tex.), and former Milwaukee County sheriff David Clarke.

“They tried to destroy Donald Trump, and they’re trying to destroy Roy Moore,” Bannon said. “There’s no bottom for how low they’ll go.”

The stakes were high for both parties, as the outcome is likely to set the stage for the 2018 midterm elections. A win in the Deep South for Democrats, the first in a Senate race in Alabama since 1992, would be a rebuke to Trump and Bannon, who have promoted Moore over the objections of establishment Republicans.

The victory would also lend credibility to Democratic efforts to regain control of the Senate next year. "The Democratic path to a Senate majority in 2018 involves a miracle somewhere," said Kyle Kondik, a political analyst at the University of Virginia Center for Politics. "And we may be on the cusp of a Democratic miracle in Alabama."

A win for Moore, in contrast, would weaken the hand of mainstream Republicans, who have struggled to broaden the party’s appeal heading into the midterms. Moore, a former state Supreme Court judge, has campaigned on a platform of opposing Senate Majority Leader Mitch McConnell (R-Ky.).

Former secretary of state Condoleezza Rice, a Republican who was born in Alabama, released a statement encouraging people to vote that seemed to rebuke Moore but stopped short of naming him.

“These critical times require us to come together to reject bigotry, sexism, and intolerance,” she wrote, before adding that voters should insist on leaders who “are dignified, decent, and respectful of the values we hold dear.”

Meanwhile, a Republican national committeewoman from Nebraska, Joyce Simmons, announced that she had resigned her post in protest of her party’s continued support for Moore, who has been accused by multiple women of sexual misconduct when they were teenagers and Moore was in his 30s.

“I strongly disagree with the recent RNC financial support directed to the Alabama Republican Party for use in the Roy Moore race,” Simmons said in an email to party leaders, who were first informed Friday of her decision. “There is much I could say about this situation, but I will defer to this weekend’s comments by Senator Shelby.”

Sen. Richard C. Shelby (R-Ala.), who voted for a write-in candidate, said Sunday that he found Moore’s accusers to be “believable” and that Moore would not represent the state well.

“I think Alabama deserves better,” Shelby said Sunday on CNN’s “State of the Union.”

Alabama Secretary of State John Merrill said he expects about 25 percent of eligible voters to cast a ballot in the special election, making the race difficult to predict. Three new polls released Monday showed dramatically different results, based on different projections of who would vote.

An automated poll from Emerson College showed Moore with a nine-point advantage, while a poll from Fox News showed Jones with a 10-point lead. A Monmouth University Poll showed the race about even.

“I’m hearing everything,” said Brian Walsh, president of America First Action, an outside group that has spent more than $1.1 million on mail, television and digital ads to support Moore. “Nobody knows what the hell is going on right now.”

Reports of the robo-calls from Obama and Biden created some awkwardness for Jones, who has tried to project distance from the national party as he closes out his campaign. Although his campaign confirmed the calls, the candidate said he was not aware of them.

“I know that there have been a lot of robo-calls that have been recorded. I don’t know what’s being used. That is just not something I’m doing,” Jones said at a campaign stop at a local restaurant, where members of the media outnumbered customers.

Giles Perkins, chairman of the Jones campaign, said about 30 different calls have gone out to voters and “most of them are local.”

A political group overseen by Biden sent out a fundraising email to supporters Monday, asking for money to help the Jones campaign.

Throughout his campaign, Jones has tried to thread a needle, portraying himself as an independent figure who is unbeholden to party leaders in an attempt to win over Republicans. At the same time, he has relied on marquee national names to help boost Democratic turnout.

Jones is waging a vigorous effort to try to turn out African American voters, who Democratic officials believe will be critical to his chances.

American Possibilities, the political group overseen by Biden, sent out a fundraising appeal Monday promising to help “support more candidates like Doug Jones.”

“We don’t need another extremist in Washington,” Biden wrote in the appeal.

Moore, who had not held a campaign event since Dec. 5, spoke in Midland City, Ala. Explaining why he didn’t campaign this weekend, Moore told the crowd: “I took approximately two and a half days to take my wife out of this mess and relax with my son at West Point.”

The entrance to a flag-draped barn was decorated with plastic alligators and greenery, meant to evoke the Washington “swamp,” and gates were set up to separate several hundred Moore supporters from special guests who’d flown in for the final stretch.

“What they’re doing to Judge Roy Moore, they’re going to try to do to every Trump supporter running for Congress next year,” said Corey Stewart, a Prince William County supervisor who is running for the Republican nomination against Sen. Tim Kaine (D-Va.) in 2018.

“We dare defend our rights,” Moore declared when he took the stage, quoting the Alabama motto that was used by state leaders in the 1960s, during the fight against desegregation. He spoke after his wife, Kayla Moore, defended his commitment to diversity.

“My husband appointed the very first black marshal to the Alabama Supreme Court,” she said. “Fake news will tell you that we don’t care for Jews. One of our attorneys is a Jew.” The media, she added, needs to be “held accountable” for how it has covered the race.

Bannon, meanwhile, making his third trip to Alabama to endorse Moore, drew boos when he mentioned Shelby and “little Bobby Corker,” a reference to regular Trump critic Sen. Bob Corker (R-Tenn.). Bannon suggested that Republican leaders might try to take out Trump “as soon as they get that tax cut” — and he even took an apparent shot at Trump’s daughter, Ivanka, who has criticized Moore.

“There’s a special place in hell for Republicans who should know better,” Bannon said, reworking a comment that Ivanka Trump had made about the misconduct allegations against Moore — one that was quickly turned into an ad by Jones.

Jones, who is focused on turning out African American voters, held a final campaign rally in Birmingham on Monday night, where he was joined on stage by basketball Hall of Famer Charles Barkley, actress Alyssa Milano and the city’s newly elected mayor, Randall Woodfin, among others.

Barkley, an Alabama native, attacked Trump, Bannon and Moore in his brief opening remarks. Moore, he said, was appealing to “the same people who’ve been holding us back for many, many years.”

In a 10-minute speech, Jones framed the election as a momentous chapter in Alabama’s history. “This election is going to be one of the most significant in our state’s history in a long time,” he said. “And we’ve got to make sure that at this crossroads in Alabama’s history, we take the right road.”

He also encouraged voters to put “decency” ahead of party loyalty and urged them to consider how Alabama will be viewed by business leaders as a result of the election.

Trump campaigned for Moore over the weekend from a distance. After touting him at a Friday evening rally just across the border in Florida, he recorded a phone call for him Saturday.

Senate Republican leaders withdrew their support of Moore in the wake of the women’s allegations. McConnell has said he expects Moore will face an immediate investigation by the Senate Select Committee on Ethics if he is elected.

A review of campaign finance records by Issue One, a group that monitors spending in political campaigns, found that $41.5 million had been spent on the Alabama special election, including funds spent on the primary and primary runoff.

Voters have been flooded with television ads about the campaign in the past few days. During one five-minute stretch on a local network Monday morning, three pro-Jones commercials and one pro-Moore ad aired.

Scherer reported from Washington. Weigel reported from Midland City, Ala. Philip Rucker and Scott Clement in Washington contributed to this report.