Democrats are fiercely trying to prevent President Trump and Senate Republicans from confirming a new Supreme Court justice before November's election, but a number of them are worried their leader on the Senate Judiciary Committee, Sen. Dianne Feinstein, D-Calif., is not up to the task.

Feinstein, 87, is currently the oldest member of the Senate, and stands to play a key role as the ranking member of the Judiciary Committee, which will vote on Trump's pick to determine if they ultimately go before the full body for a confirmation hearing.

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"She’s not sure what she’s doing," one Democratic senator told Politico, expressing concern that Feinstein could make costly errors that impact not only the Supreme Court but the party's Senate future.

Feinstein faced criticism during the contentious confirmation process of Justice Brett Kavanaugh. Allegations of attempted sexual assault from Dr. Christine Blasey Ford nearly derailed Kavanaugh's confirmation, but when it was discovered that Feinstein learned of the allegations prior to his hearing and did nothing until a report came out about it, it raised questions about Democrats' motives.

"If you take a look at Kavanaugh, we may be short two senators because of that," the senator added. "I think it could impact a number of seats we can win."

The senator said that there are several others who would rather see Feinstein replaced by someone like Sen. Dick Durbin, D-Ill., or Sen. Sheldon Whitehouse, D-R.I., as the Judiciary ranking member for the upcoming confirmation process.

"She can't pull this off," a second senator told Politico.

A third senator told the outlet that the party was "in an impossible position" because they could not remove a woman from power as Trump is expected to nominate a woman to the Supreme Court.

One of the favorites for the appointment is Judge Amy Coney Barrett, who had a now-infamous exchange with Feinstein during her confirmation hearing for the 7th U.S. Circuit Court of Appeals.

Feinstein was critical of Barrett's faith, citing speeches she delivered at the University of Notre Dame -- a Catholic school where Barrett taught -- implying that as a devout Catholic she was incapable of fairly applying the law.

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"I think in your case, professor, when you read your speeches, the conclusion one draws is that the dogma lives loudly within you,” Feinstein said. “And that’s of concern."

Feinstein and other Democrats were chastised by Sen. Ben Sasse, R-Neb., who referenced the prohibition against religious tests.

"I think some of the questioning that you have been subjected to today seems to miss some of these fundamental constitutional protections we all have," Sasse said at the time.

Some prominent Democrats remain supportive of Feinstein.

"She’s an extraordinary person and I’m fully confident in her leadership,” Sen. Cory Booker, D-N.J., told Politico. Sen. Richard Blumenthal, D-Conn., said Feinstein's leadership was "really steadfast and courageous" and sees "no reason to question this leadership."

Feinstein told Politico that she was "surprised" by the doubts some of her colleagues have regarding her capability to lead them through the upcoming confirmation battle.

“I’m really surprised and taken aback by this. Because I try to be very careful and I’m puzzled by it,” Feinstein said. “My attendance is good, I do the homework, I try to ask hard questions. I stand up for what I believe in.”

"And so it's difficult for me to see, I don't know what people expect,” she added. “I’ve been on the committee for a while. I’ve seen how the committee works and I’ve seen how other chairs on our side of the aisle work. I don’t see, to be very blunt and honest, I don’t see a big difference. I’m prepared, so that’s puzzling to me.”

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Ultimately, however, Feinstein said that there is not much that can be done because Republicans have the majority and as long as they are united they can do what they please. Still, she said she will do whatever she can to stand in their way.

"I don’t have a lot of tools to use, but I’m going to use what I have," she said. "We can try to delay and obstruct but they can run this process through. That doesn’t mean that we won’t fight tooth and nail."