Sen. Rob Portman Robert (Rob) Jones PortmanMcConnell locks down key GOP votes in Supreme Court fight Romney undecided on authorizing subpoenas for GOP Obama-era probes Congress needs to prioritize government digital service delivery MORE (R-Ohio) is signaling that he would consider a Supreme Court nominee from Hillary Clinton Hillary Diane Rodham ClintonButtigieg stands in as Pence for Harris's debate practice Senate GOP sees early Supreme Court vote as political booster shot Poll: 51 percent of voters want to abolish the electoral college MORE after a GOP colleague pledged united opposition this week.

"I look at each one on the merits," Portman said during a Senate debate in Cleveland on Thursday night. "So no, I don't agree that we should automatically block nominees."

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Portman added that he would back a "fair hearing process" and noted that he's supported some of President Obama's nominees.

"I think we should look at justices on the merits and I'll look at justices as to wether they are faithful to the Constitution, whether they're going to legislate from the bench ... and what their qualifications and background are," he said.

The focus on a potential Clinton nomination comes after Sen. John McCain (R-Ariz.) told a Philadelphia radio station that Senate Republicans would be "united against" her pick.

Though his staff later clarified that he would consider any nominee, McCain's comments sparked criticism from some Democrats and outside groups that Republicans would refuse to take up a Supreme Court nominee if Democrats keep control of the White House after Election Day.

Sen. Pat Toomey (R-Pa.) separately told the PennLive editorial board that while he believes McCain misspoke, he doesn't agree with McCain's initial comments.

McCain, Grassley, Toomey and Portman are all up for reelection in November.

Former Gov. Ted Strickland, Portman's Democratic opponent, argued Thursday that the Ohio senator is already holding up a Supreme Court nominee, pointing to the GOP blockade over Obama's pick, Merrick Garland.

"For months he has blocked Judge Garland. He said this man should not have a hearing or get a vote. He has disrespected the president," Strickland said. "He has not done his job for months."

Republicans argue the Senate shouldn't take up a Supreme Court nomination during an election year and that the next president should be able to fill the vacancy following Justice Antonin Scalia's death in February.