President Trump is determined to fill the vacancy created by Supreme Court Justice Ruth Bader Ginsburg’s death and setting up a historic, election-year battle over who will succeed her.

Trump said Saturday that he expects to announce his replacement for Ginsburg within a week and that his choice will be a woman. But the president has a tendency to change his mind, and sources have cautioned that the selection process is fluid and moving quickly.

Ginsburg, a revered champion for women’s rights and liberal leader on the high court, died from pancreatic cancer on Friday. Her death immediately injected new uncertainty into the election, which is six weeks away, and ignited a debate surrounding whether, and how quickly, Republicans should move to fill her seat.

Here are some candidates who are most likely the top contenders for the seat:

Amy Coney Barrett-Barrett, 48, was immediately viewed as a front-runner to replace Ginsburg as Republicans signaled they would quickly move to fill the seat.

“She’s very highly respected. I can say that,” Trump told reporters Saturday before departing the White House for a Fayetteville, N.C., rally when asked about Barrett.

Barrett, a former clerk for late Supreme Court Justice Antonin Scalia, was nominated by Trump and confirmed in a 55-43 vote by the Senate to serve on the U.S. Court of Appeals for the 7th Circuit in 2017. At the time, three Democratic senators supported her nomination: Joe Donnelly, who subsequently lost his 2018 reelection bid, Tim Kaine and Joe Manchin

Barrett is viewed as a favorite among conservatives and was included on the shortlist to succeed former Justice Anthony Kennedy when Trump ultimately selected then-D.C. Circuit Judge Brett Kavanaugh. Axios reported in 2019 that Trump told aides he was “saving” Barrett as a potential replacement for Ginsburg.

But picking Barrett would further inflame America’s partisan culture war weeks before an election. She would face scrutiny over her previous statements on ObamaCare’s birth control mandate, which she called a “grave violation of religious freedom,” and her criticism of the Supreme Court’s landmark ruling in Roe v. Wade and deference to legal precedent.

Barbara Lagoa– Lagoa, 52, is a Cuban American judge and native of Florida. She, like Barrett, is viewed as a strong contender to replace Ginsburg.

Lagoa was nominated by Trump to serve on the U.S. Court of Appeals for the 11th Circuit at the end of 2019. She was confirmed by the Senate in a rare bipartisan vote of 80-15, winning support from 26 Democrats, including Senator  Dianne Feinstein, the top Democrat on the Senate Judiciary Committee.

Lagoa has an extensive legal background and has been a judge in state and federal courts. Her potential nomination could also have a political upside for Trump given that she is a Cuban American from the key battleground state of Florida, where public polling shows a close race between Trump and Democratic presidential nominee Joe Biden.

“She’s an extraordinary person. I’ve heard incredible things about her. I don’t know her. She’s Hispanic and highly respected,” Trump told reporters Saturday when asked about Lagoa.

Lagoa would likely face renewed questions from Democrats over her decision not to recuse herself from a case involving felon voting rights in Florida that she previously participated in as a state judge. The case eventually reached the full bench of the 11th Circuit Court, where Lagoa joined the court’s 6-4 majority decision to uphold a Florida law requiring nearly 800,000 former felons in the state to settle their court debt before they regain the right to vote, even if they are unable to pay.

“Your participation … appears to contradict your commitment to recuse yourself from any case in which you participated during your time on the Florida Supreme Court,” Senate Judiciary Committee Democrats wrote in a letter to Lagoa about her decision.

Before her nomination to the federal appeals court, Lagoa was appointed by Florida Governor Ron DeSantis to the Florida Supreme Court, becoming the first Hispanic woman and Cuban American woman to be appointed to serve as a justice on the court.

If nominated by Trump to serve on the U.S. Supreme Court, Lagoa would become the second Latino justice, following current liberal Justice Sonia Sotomayor.

Allison Jones Rushing– While Barrett and Lagoa have been cited as top contenders, Rushing’s name is also in the mix.

At the age of 38, Rushing would be an extremely young nominee to serve on the high court. In comparison, the youngest member of the current eight justices is Neil Gorsuch, who is 53. Supreme Court justices are, on average, in their early 50s when confirmed, according to data compiled by Quartz, which tracked confirmations back to the late 1700s.

Rushing was nominated by Trump to serve on the U.S. Court of Appeals for the 4th Circuit in 2018 and confirmed by the Senate the following year in a vote of 53-44 that fell along party lines.

Senate Democrats painted Rushing as woefully inexperienced and raised red flags over past remarks that appeared hostile to Supreme Court decisions that expanded the rights and protections of LGBTQ people. She also came under fierce scrutiny for her ties to the Alliance Defense Fund, a conservative Christian group she interned for that the Southern Poverty Law Center considers an anti-LGBTQ hate group.

She previously clerked for Supreme Court Justice Clarence Thomas as well as Gorsuch when he served on the 10th Circuit.

Here are a few other names that have potential:

Amul Thapar: Thapar, the son of Indian immigrants, would be the first Asian justice on the U.S. Supreme Court. Thapar, 51, currently sits on the Cincinnati-based 6th Circuit, which has jurisdiction over several Midwest states, after spending nearly a decade as a George W. Bush appointee to a federal trial court in Kentucky.

Prior to joining the federal bench, Thapar held various positions as a lawyer in government and private practice. As a U.S. prosecutor, Thapar successfully prosecuted a series of mortgage fraud cases in Ohio and busted a criminal scheme to provide government identification to illegal aliens.

Thapar has provided pro bono representation to the Becket Fund for Religious Liberty, a major advocacy group that promotes religious rights, and considers himself an originalist and textualist, the style of judging most closely associated with the late Justice Scalia.

Thomas Hardiman: Hardiman sits on the Philadelphia-based U.S. Court of Appeals for the 3rd Circuit, and he was considered for both of the vacancies left by Scalia and Kennedy. Those nominations went to Gorsuch and Kavanaugh, respectively.

Trump’s sister, Maryanne Trump Barry, served with Hardiman on the 3rd Circuit and reportedly recommended him to the president as a potential Supreme Court nominee.

Hardiman, 55, was nominated to serve on the federal bench by Bush in 2003, and he was nominated to serve on the 3rd Circuit in 2007. He has established a reputation for his conservative rulings, and his personal story — he is the first in his family to graduate from college — is said to have resonated with Trump.

Bridget Bade: If the president follows through on his commitment to picking a woman, he may look elsewhere on his recently expanded list of potential nominees.

Bade, who sits on the U.S. Court of Appeals for the 9th Circuit, was added to the list earlier this month. Trump nominated her to the federal bench first in 2018 and again in early 2019 when the new Congress was seated. She was confirmed in March 2019 by a bipartisan vote of 78-21.