Pennsylvania Lt. Gov. John Fetterman and celebrity doctor Mehmet Oz are locked in a tight race for a U.S Senate seat that could determine which party controls that chamber in 2023.

Multiple polls show Fetterman, a Democrat, and Oz, a Republican, neck and neck in a heated battle for the seat held by retiring Republican Sen. Pat Toomey. Observers rate the race a toss-up.

Both candidates brought in heavy hitters to boost their chances in the final weekend before the Nov. 8 election.

Former President Donald Trump stumped for Oz on Nov. 5 in Latrobe, while also teasing another presidential run in 2024. Trump told the crowd a Fetterman win "will mean death and despair" for the state’s residents and that "Dr. Oz is the only one who can stop him."

Fetterman, meanwhile, brought in the current and former president to tout his candidacy.

Barack Obama appeared with Fetterman on Nov. 5 at a Pittsburgh rally and later joined Fetterman and President Joe Biden at a rally in Philadelphia. Obama accused Republicans of resorting to fear tactics to win, while Biden said the midterm election "is going to shape our country for decades to come." 

Even Oprah Winfrey got involved, endorsing Fetterman over Oz, whose television career she helped launch. Winfrey frequently featured Oz on her talk show, and her company, Harpo Productions, co-produced "The Dr. Oz Show." Winfrey was silent about Oz’s race for more than a year, before declaring support for Fetterman during a virtual town hall Nov. 3.

Here are some of our fact-checks and stories in this important race.

A narrator in an ad by Planned Parenthood Votes said that Republican senators want to ban abortion nationwide and that they’d need Oz to do it. But the ad leaves out important context about Oz’s position, we found.

Oz supports the Supreme Court decision that overturned Roe v. Wade and returned abortion regulations to the states. However, he also supports abortion exceptions in cases of rape or incest or if the mother’s life is endangered. He does not support a federal abortion ban.

"I want women, doctors, local political leaders, letting the democracy that’s always allowed our nation to thrive to put the best ideas forward so states can decide for themselves," Oz said Oct. 25 in a debate with Fetterman. 

This is Mostly False.

Gingrich, the former Republican House speaker, claimed that tattoos on Fetterman’s arms are references to heroin use and violent gangs.

According to Fetterman, that’s not the story behind the ink. The number "15104" tattooed on his left arm is the ZIP code for Braddock, Pennsylvania, the Pittsburgh suburb where Fetterman was mayor from 2006 to 2019.

Tattoos on his right arms are numeric dates that Fetterman said are meant to memorialize Braddock residents who died in violent crimes while he was mayor. He also used to have a tattoo with the words "I will make you hurt" — which is a lyric from a Nine Inch Nails song that refers to needle use. Fetterman said in a 2009 interview that the words were connected to the pain he felt about those residents killed in violent crimes.

This is Half True.

An ad focused on animal experiments done at a Columbia University research lab that Oz supervised years ago to accuse him of animal cruelty.

Oz’s campaign didn’t dispute a report that more than 300 dogs were euthanized in experiments from 1989 to 2010, but noted the work was done by students and postdoctoral fellows, and that veterinarians cared for the animals. 

The ad focused on a dog known as 6313, which it said suffered greatly in the heart research experiments. But an internal investigation by the university found that the dog, which lost blood and had difficulty breathing, was given "appropriate veterinary care."

This is Mostly True.

A political ad detailed a 2013 incident when Fetterman was the mayor of Braddock. Fetterman said then that he thought he heard a dozen gunshots near his home and called 911. He then chased a Black man named Chris Miyares, who he thought had fired them. He displayed a shotgun to hold the man until police arrived. It’s unclear whether Fetterman knew Miyares was Black before he chased him.

Police said Miyares was wearing exercise clothes and earphones. He was unarmed and they released him without charges. 

We rated each of these claims made in ads approved by Oz as Mostly False.

Fetterman has called for reversing a Pennsylvania law that mandates life-without-parole sentences for people convicted of second-degree murder, even if they are only accessories in a killing. In such cases, people involved in a felony crime such as a robbery that results in a death could be sentenced to life in prison, even if they were not directly responsible for the death.

Fetterman argued it’s unjust to give an accomplice in a crime the same sentence as the person convicted in the killing. Oz’s ad distorts that position to make it seem as if Fetterman called to end life sentences for all murderers.

The same ad also misleads about Fetterman’s position on releasing criminals. He has not called for the release of one-third of "dangerous criminals." In 2020, Fetterman said he agreed with a statement he attributed to Pennsylvania's then-corrections secretary that the state could reduce its prison population by one-third without risking public safety.

RELATED: A brief history of Senate illness and recovery, and what it means for John Fetterman