Republican Sens. Susan Collins and Lisa Murkowski once again have a chance to decide whether President Donald Trump reaches one of his key goals.

The senators will be swing votes in a narrowly divided Senate on whether to confirm the judge Trump picks to fill retiring Justice Anthony Kennedy's seat on the Supreme Court. Their votes could hinge on whether the top court nominee signals support for upholding precedent on Roe v. Wade, the landmark 1973 decision legalizing abortion nationally. Kennedy's departure has raised fears among abortion rights advocates that the new court could weaken or overturn the decision.

The confirmation process again sets the Republican senators up as foils after they bucked GOP leaders and Trump to help sink the party's Obamacare repeal plan last year. If Democrats unite in opposition to Trump's choice — which they did not do when the Senate confirmed Justice Neil Gorsuch last year — one Republican defection would doom the judge's confirmation.

Both Collins and Murkowski have generally supported abortion rights. Trump's choice could be a person hostile to the Roe ruling, as conservatives will vet and give advice on the potential nominees.

As a candidate in 2016, Trump pledged to appoint judges who would overturn Roe v. Wade. Also during the campaign, he said, "There has to be some form of punishment" for women who get abortions.

In interviews Sunday, Collins said she would not favor a Supreme Court choice who has shown opposition to the Roe decision.

"I would not support a nominee who demonstrated hostility to Roe v. Wade because that would mean to me that their judicial philosophy did not include a respect for established decisions, established law," the Maine Republican told CNN.

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Collins met with the president and told him she would not back some of the people on his existing shortlist of 25 candidates, she separately told ABC News. The senator urged Trump to expand his list.

Trump plans to announce his pick July 9. If confirmed, the justice would set the court's balance at five judges appointed by Republican presidents and four chosen by Democrats. While Republican President Ronald Reagan picked Kennedy, he joined four other justices in 1992 in a ruling upholding Roe v. Wade.

Collins said she believes both Chief Justice John Roberts and Gorsuch, the Trump-appointed conservative, would respect legal precedent on the abortion rights decision. However, that is not assured, even though the judges have generally expressed support for established law.