WASHINGTON, July 1 (Reuters) - A key moderate Republican U.S. senator said on Sunday she will not support a nominee to fill a soon-to-be-vacated seat on the Supreme Court who would overturn a key legal ruling that supports a woman's right to abortion.
"I would not support a nominee who demonstrated hostility to Roe v Wade," Susan Collins told CNN's "State of the Union" program, referring to the 1973 landmark decision.
Collins of Maine is a frequent swing vote in the Senate, which Republicans control by a slim majority.
The Senate must approve any nominee from Republican President Donald Trump to replace Supreme Court Justice Anthony Kennedy, who is retiring at the end of July.
RELATED: History of Roe v. Wade
History of Roe v. Wade
History of Roe v. Wade
(Original Caption) 4/6/1989-Denver, CO- Brandishing homemade signs, hundreds of pro-choice advocates attend a rally in Downtown Denver to show their support for a woman's right to a legal abortion. The rally was staged to coincide with arguments held in the U.S. Supreme Court that could overturn the landmark Roe V. Wade decision.
BURBANK, CA - JULY 4 : Attorney Gloria Allred and Norma McCorvey (R),'Jane Roe' plaintiff from Landmark court case Roe vs. Wade during Pro Choice Rally, July 4, 1989 in Burbank, California. (Photo by Bob Riha, Jr./Getty Images)
Associate Justice Harry Blackmun of the US Supreme Court said that the abortion decision he wrote a year ago, 'will be regarded as one of the worst mistakes in the court's history or one of its greatest decisions, a turning point.' But he said it was 'a case the Court couldn't win, because the country is so evenly divided on the subject' and both sides feel so strongly about it. The usually reticent jurist made the remarks in an informal chat with newsmen at St. Paul Mechanic High School. The case he is speaking of is 1973 Roe vs.Wade, when he ruled for the Supreme Court that states may not ban abortions in the first six months of pregnancy.
(Original Caption) Washington: Norma McCorvey, 'Jane Roe' in Roe vs. Wade is the center of the media attention following arguments in a Missouri abortion case at the Supreme Court. McCorvey attended the session as a spectator.
A group of anti abortionists hold a 'March for Life' banner during a rally on the Supreme Court anniversary of Roe vs. Wade in Washington DC. (Photo by ?? Leif Skoogfors/CORBIS/Corbis via Getty Images)
Pro-life demonstrators with signs imploring everyone to 'Pray and Fast for God to End Abortion.' The protesters hope are lobbying the Supreme Court to overturn Roe vs. Wade and end women's right to abortion. (Photo by ANDREW HOLBROOKE/Corbis via Getty Images)
Portrait of Norma McCorvey (Jane Roe in famous law suit Roe v. Wade)) after she admitted she had not been gang raped when she sought an abortion in 1970. (Photo by Cynthia Johnson/The LIFE Images Collection/Getty Images)
The largest pro-choice rally to ever assemble against any possible Supreme Court reversal of Roe v. Wade decision. Women display a 'Keep Abortion Legal' sign in front of the Washington Monument. (Photo by ANDREW HOLBROOKE/Corbis via Getty Images)
399974 05: Pro-life activists Lori Gordon (R) and Tammie Miller (L) of Payne, OH take part in the annual 'March for Life' event January 22, 2002 in Washington, DC. Activists marched from the Washington Monument to the U. S. Supreme Court in commemoration of the 29th anniversary of Roe vs. Wade. The Roe vs. Wade January 22, 1973 Supreme Court decision legalized abortion in the United States. (Photo by Alex Wong/Getty Images)
399974 03: (L-R) Seminarians Jeremy W. Sell and Eddie Radler of Mount Saint Marys Seminary in Emmitsburg, MD sing prayers as they hold up the statue of the Virgin Mother during the annual 'March for Life' event January 22, 2002 in front of the U.S. Supreme Court in Washington, DC. Activists marched from the Washington Monument to the U.S. Supreme Court in commemoration of the 29th anniversary of Roe vs. Wade. The Roe vs. Wade January 22, 1973 Supreme Court decision legalized abortion in the United States. (Photo by Alex Wong/Getty Images)
DENVER,CO--Samuel Doran, 6, with the help of his father, Peter, (not seen, just hand) holds up a pro life sign at the 2003 March for Life rally at on the west steps of the Captiol saturday afternoon commemorating the 30th Anniversary of Roe v. Wade. THE DENVER POST/ ANDY CROSS (Photo By Andy Cross/The Denver Post via Getty Images)
An anti-abortion activist hold a sign in front of the Supreme Court on January 22, 2003. Anti-abortion and pro-abortion activists marched in Washington for the March of Life as part of a day long rememberance of the 1973 Roe vs. Wade ruling that made abortion legal. (Photo by mark peterson/Corbis via Getty Images)
Sarah Phares, a nurse at an abortion clinic in Wichita, Kansas, holds up a flyer that was sent to her in the mail, demanding that she quit her job. Although afraid to reveal her identity, she is more committed than ever to working at the clinic, and receives a salary bonus whem anti-abortion activists picket her house. (Photo by Andrew Lichtenstein/Corbis via Getty Images)
WASHINGTON, UNITED STATES: Pro-choice supporter and intern with the National Organization for Women, Meredith Harper, smiles as she ignores the pleadings of pro-life protesters that abortion is wrong in front of the US Supreme Court during the March for Life demonstration 22 January, 2004, in Washington, DC. US President George W. Bush praised anti-abortion marchers for their 'noble cause' as Democrats in Congress introduced a bill to block US government interference in reproductive rights. The annual march takes place every 22 January, the anniversary of the 1973 Roe vs. Wade Supreme Court decision legalizing abortion. AFP PHOTO / TIM SLOAN (Photo credit should read TIM SLOAN/AFP/Getty Images)
SAN FRANCISCO - JANUARY 22: Two women carry a sign during a pro-choice march January 22, 2004 in San Francisco. People all over the United States celebrated the 31st anniversary of the 1973 Roe vs. Wade Supreme Court decision legalizing abortion.(Photo by Justin Sullivan/Getty Images)
NEW YORK - JULY 20: Pro-choice women protest U.S. President George W. Bush's nominee for the Supreme Court John G. Roberts Jr. in Union Square July 20, 2005 in New York City. Pro-choice activists are troubled that Roberts went on the record calling for Roe v. Wade to be overturned when he served as a lawyer for the government. (Photo by Mario Tama/Getty Images)
WASHINGTON - JULY 19: Bethany Kontur, an activist with the group Bound For Life, prays in front of the Supreme Court July 19, 2005 in Washington, DC. President Bush is expected to announce his Supreme Court nominee later this evening - an event that could have significant impact on the Roe vs. Wade decision and other legal cases. (Photo by Win McNamee/Getty Images)
WASHINGTON - JANUARY 23: Members of the Silent No More organization join thousands of anti-abortion demonstrators during the March for Life to mark the 33rd anniversary of the landmark Supreme Court case Roe v. Wade January 23, 2006 on the National Mall in Washington, DC. The demonstrators marched up to Capitol Hill and the Supreme Court after President George W. Bush spoke to the marchers via telephone, telling them the Declaration of Independence protects the weak and the sick. 'Especially unborn children,' Bush said. (Photo by Chip Somodevilla/Getty Images)
Washington, UNITED STATES: Pro-choice demonstrators wave signs in front of the US Supreme Court 30 November 2005, in Washington,DC.The US Supreme Court prepared to take up an abortion case for the first time in five years on 30 November, in a test of new chief justice John Roberts on a hotly contested issue.The high court's landmark 1973 Roe v. Wade decision legalized abortion nationwide, while individual states have put in place their own restrictions.The court will hear arguments on a 2003 New Hampshire law requiring minors tell at least one of their parents 48 hours before having an abortion. The only exception is if the girl's life is threatened. Opponents of the law say that exception is not enough. They want girls to be able to obtain an abortion immediately without prior parental permission in cases of medical emergency. Minors seeking abortions must inform their parents in about 30 US states, and in some must seek parental permission. AFP PHOTO/KAREN BLEIER (Photo credit should read KAREN BLEIER/AFP/Getty Images)
WASHINGTON - JANUARY 23: 'Defend Life' signs are stacked and given away free to thousands of anti-abortion demonstrators during the March for Life to mark the 33rd anniversary of the landmark Supreme Court case Roe v. Wade January 23, 2006 on the National Mall in Washington, DC. The demonstrators marched up to Capitol Hill and the Supreme Court after President George W. Bush spoke to the marchers via telephone, telling them the Declaration of Independence protects the weak and the sick. 'Especially unborn children,' Bush said. (Photo by Chip Somodevilla/Getty Images)
WASHINGTON - JANUARY 22: Marchers participating in the annual March for Life pass the U.S. Supreme Court building January 22, 2007 in Washington, DC. Activists from across the nation gathered to commemorate the 34th anniversary of the Roe v. Wade Supreme Court decision, which decriminalized abortion in all fifty states. (Photo by Mark Wilson/Getty Images)
Pro-life activist Norma McCorvey poses in a Smithville, TX park on a sweltering summer afternoon. McCorvey, who was 'Jane Roe' in the 1973 Supreme Court case of Roe vs. Wade that struck down many state laws that restricted abortion, has led an eventful and fascinating life on both sides of the issue. | Location: Smithville, Texas, USA. (Photo by Robert Daemmrich Photography Inc/Corbis via Getty Images)
WASHINGTON, DC - JANUARY 23: Sara Brook, of Missouri, points her finger at a pro choice protestor. Brook is pro life. The annual March for Life Rally marks the anniversary of the Roe v. Wade decision by the Supreme Court. The event was held in Washington, DC on Monday. (Photo by Sarah L. Voisin/The Washington Post via Getty Images)
WASHINGTON - JANUARY 23: Pro-choice activists with the National Organization For Women hold a vigil outside the U.S. Supreme Court on January 23, 2012 in Washington, DC. The vigil was held to mark the anniversary of the Roe v. Wade Supreme Court decision that legalized abortion. (Photo by Brendan Hoffman/Getty Images)
PITTSBURGH, PA - DECEMBER 29: In Pittsburgh, PA, abortions are routinely done at the Allegheny Reproductive Health Center as the 40th anniversary of Roe vs. Wade is marked this month. A Medical Assistant prepares a procedure room at the beginning of the day.(Photo by Sarah L. Voisin/The Washington Post via Getty Images)
WASHINGTON, DC - JANUARY 25: An anti-abortion protester holds a crucifix at the March for Life on January 25, 2013 in Washington, DC. The pro-life gathering is held each year around the anniversary of the Roe v. Wade Supreme Court decision. (Photo by Brendan Hoffman/Getty Images)
Pro-life activists protest in front of the White House on January 21, 2014 in Washington, DC. Pro-life activists gather each year to protest on the anniversary of the Roe v. Wade Supreme Court decision that legalized abortion. AFP PHOTO/Jewel SAMAD (Photo credit should read JEWEL SAMAD/AFP/Getty Images)
Pro-choice activists holds a coat hanger, historically used for self-induced abortion, that reads 'never again' in front of the US Supreme Court in Washington, DC, January 22, 2015, during the March For Life rally. Tens of thousands of Americans who oppose abortion are in Washington for the annual March for Life, marking the 42nd anniversary of the Supreme Court's Roe v. Wade decision. AFP PHOTO/JIM WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)
A pro-choice activists holds a placard in front of the US Supreme Court in Washington, DC, January 22, 2015, as she and others await the pro-choice activists with the March For Life. Tens of thousands of Americans who oppose abortion are in Washington for the annual March for Life, marking the 42nd anniversary of the Supreme Court's Roe v. Wade decision. AFP PHOTO/JIM WATSON (Photo credit should read JIM WATSON/AFP/Getty Images)
UNITED STATES - JANUARY 22: Sarah Tressler of Alexandria, and her daughter Juliette, 7 months, walk past the Capitol on Constitution Avenue during the annual March for Life, to protest the Supreme Court's Roe v. Wade decision to legalize abortion, January 22, 2015. This is the 42nd anniversary of the decision which was handed down by the court on January 22, 1973. (Photo By Tom Williams/CQ Roll Call)
UNITED STATES - JANUARY 22: Pro-life protesters wearing ski goggles march in front of the U.S. Supreme Court on the anniversary of Roe v. Wade Friday, Jan. 22, 2016. The annual March for Life went ahead as planned despite the blizzard warnings issued for the DC area. (Photo By Bill Clark/CQ Roll Call)
Discover More Like This
BACK TO SLIDE
Trump said on Friday he plans to announce his nominee to the nation's highest court on July 9 and has narrowed his list of candidates to about five, including two women.
"I told [President Trump] that I was looking for a nominee that would demonstrate a respect for precedent ... I also suggested that he broaden his search," Collins also told ABC's "This Week" program.
She added that there were people on Trump's initial list that she could not support.
Trump has said he will not ask candidates whether they would overturn the 1973 Roe v. Wade decision, which established a woman's right to abortion.
While Kennedy was a conservative, he proved to be a somewhat unpredictable "swing" vote over his long career. He sided with the court's liberals by voting in favor of abortion rights and gay rights in key cases.
Views on abortion were expected to be a topic that senators will ask the new nominee about in confirmation hearings - even if the president does not.
In addition to Collins, another key vote in the Senate on the abortion issue would be fellow Republican Senator Lisa Murkowski, who also favors abortion rights. (Reporting by Lindsay Dunsmuir Editing by Kevin Drawbaugh, Lisa Shumaker and Jeffrey Benkoe)