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In a tense exchange between Amy Coney Barrett and Sen. Dianne Feinstein in 2017, the California Democrat sharply questioned whether the judicial nominee could separate her Catholic views from her legal opinions.

“The conclusion one draws is that the dogma lives loudly within you,” Feinstein pointedly said. “And that’s of concern when you come to big issues that large numbers of people have fought for years in this country.”

The exchange became a rallying cry for Republicans – and quickly put Democrats on the defensive as the GOP accused them of creating a religious litmus test for President Donald Trump’s nominee to sit on the 7th US Circuit Court of Appeals. Democrats said the exchange was in reference to Barrett’s own writings on the topic that had prompted questions from both parties – and concerns from progressives that she would chip away at abortion rights.

Now Barrett appears to be the front-runner for Trump’s Supreme Court nominee. And Democrats are beginning to discuss how to avoid such pitfalls when they face off against the President’s nominee in confirmation hearings as soon as next month, recognizing that’s likely their lone shot at derailing a conservative jurist who could tilt the ideological balance of the court for decades to come.

“I never really focused on religious beliefs. They are really, in my view, irrelevant to her qualification,” Sen. Richard Blumenthal, a Connecticut Democrat who’s a member of the Senate Judiciary Committee, said Tuesday. “Everybody’s entitled to believe or practice and worship as they like. My focus is on substantive issues.”

But asked if her religious views should be off-limits if Barrett comes before the committee again, Sen. Mazie Hirono said: “No.”

“Look, it wasn’t her religious views – it’s anybody’s views that they bring to their decision making,” said Hirono, a Hawaii Democrat who’s also a member of the committee. “So they keep telling us that none of the things they wrote or said yesterday should infringe on their decision, but how can we be assured that they can be objective? … Why should we say you get a lifetime appointment so that you can reflect your ideological agenda in your decision making?”

Asked if she would pursue that line of questioning again, Feinstein declined to say: “I’m not going to go there.” She added, “Let’s wait till she’s nominated,” when asked how Democrats would target a Barrett nomination.

Democratic strategy: Focus on health care and avoid talk of packing courts

The debate underscores the challenge facing Democrats as they try to nail down the right strategy to battle a nomination that appears to be on the glide path to confirmation on the backs of Republicans.

On private conference calls in the aftermath of the death last week of Justice Ruth Bader Ginsburg, Democrats have had a wide-ranging discussion about their plans and tactics.

Overwhelmingly, they believe they must focus their message on how the new nominee would jeopardize the health care of millions, with the constitutionality of the Affordable Care Act before the Supreme Court and persistent court challenges against abortion rights. They also believe they should focus on what they view as a blatant power grab by the GOP to jam a nominee through on the eve of a national election, contradicting the Republican refusal to move on President Barack Obama’s Supreme Court nominee eight months before the 2016 election.

And increasingly, Democrats are trying to steer clear of talk that they would change the makeup of the Supreme Court by adding seats to it if they take the Senate majority this fall, with some arguing that gives the GOP ammunition in the battle for control of the chamber.

“I’m not for retaliatory moves,” said Sen. Doug Jones of Alabama, the Democrats’ most vulnerable senator this cycle, pushing back on calls to add seats to the court. He wouldn’t say if he would oppose a Trump pick no matter what.

Sen. Jeanne Shaheen of New Hampshire, who also faces voters in November, said: “No” when asked if she backs adding more seats to the court if Democrats take the majority.

“I think the important thing right now is that people need to make our Republican colleagues and the Trump administration aware … if they believe, as I do, that they should let the election go forward and the next president, whoever that is, nominate the nominee to the Supreme Court,” Shaheen said.

Sen. Elizabeth Warren, a Massachusetts Democrat and progressive firebrand, sidestepped questions when asked if she favored adding seats to the Supreme Court.

“We need to talk about what’s at stake now: What’s at stake in the lives of millions and millions of families,” Warren said Tuesday.

Others declined to weigh in. “With the mask, I can’t even hear you,” Sen. Kyrsten Sinema of Arizona told a reporter within earshot when asked about her views on adding seats to the court, as she walked onto an elevator.

Democrats who backed Barrett to appeals court already a ‘no’

When Barrett was confirmed to her current post, just three Democrats voted for her – Sens. Tim Kaine of Virginia, Joe Manchin of West Virginia and Joe Donnelly of Indiana, who lost his race in 2018. But Kaine and Manchin told CNN on Tuesday that they would vote against Barrett now if she gets the nomination, over concerns about the GOP effort to confirm a nominee with less than two months before Election Day.

Asked why he had voted for Barrett in 2017, Kaine said: “I think I needed a reason to vote no. So I voted yes because she had a distinguished record and, watching her performance at the committee, I think she was entitled to her position based on her record.”

But Kaine added that if she’s nominated now, “I’m not going to vote for a nominee of an illegitimate process. And I don’t care who it is. It could be Aaron Judge or Judge Judy, I’m not gonna vote for somebody that’s put up in an illegitimate process.”

Manchin told CNN: “I’d be no on everything. From a standpoint it’s just wrong. … This is the poster child for hypocrisy right now.”

But he had a warning for his party when asked about the Feinstein-Barrett exchange from the previous hearing.

“I’m Catholic, OK?” Manchin said. “Religion should not play a part. … I don’t know why that was ever brought up. And she’s, she believes what she believes; I believe what I believe.”

Barrett’s writing sparked scrutiny

Democrats on the Senate Judiciary Committee have yet to discuss their strategy in depth given that Trump has yet to name his pick, but they are already familiar with Barrett’s record.

Indeed, Barrett’s past writings are bound to come up. In the hearing, Democrats and Republicans questioned her about a 1998 law article she had co-written, which said: “The Catholic Church’s opposition to the death penalty places Catholic judges in a moral and legal bind.”

“It seems to us, then, that the proper approach to this kind of case morally and legally – is for the observant Catholic judge to recuse himself after trial and before the sentencing hearing,” the article said. “It would probably be appropriate to give the parties prior notice that he intends to do so if the trial ends in conviction.”

Dick Durbin of Illinois, a member of the Senate Judiciary Committee and the second-ranking Senate Democrat, defended that line of questioning on Tuesday, noting that senators in both parties had questions about that article.

“She raised the issue. She was questioned by four different senators: two Democrats, myself included, and two Republicans. What did she mean by this? Ordinarily, you would never raise the question of religion in a hearing,” Durbin said.

At the hearing, Barrett testified that her religious beliefs would not interfere with her rulings as a federal judge.

But Democrats, including Feinstein, were not convinced, worried that Barrett’s views meant that she would strike against abortion rights as a federal judge.

And some Republicans seem to agree about her views on abortion.

Republican Sen. Josh Hawley of Missouri, who has said his support for a Supreme Court justice is contingent on whether the nominee believes Roe v. Wade is “wrongly decided,” said Barrett meets that test.

“I think she meets that standard,” Hawley said.

The topic is bound to dominate hearings if Barrett gets the nod.

But Democrats are arguing they have to tread carefully around the topic of faith.

Sen. Sheldon Whitehouse, a Democrat from Rhode Island who’s on the committee, said Tuesday that “a person’s religious views or background should not make any difference so long as it’s clear that they can leave that personal background at the robing room door, and give impartial justice to whomever is before them irrespective of whether the personal religious views might dictate something different than the law.”

When the hearings happen, Durbin said, Democrats need to “take care that we respect the Constitution, that we ask her probative questions, respectful questions and make certain the American people understand where any nominee stands.”

The GOP decision to press ahead with the nomination despite taking the opposite view four years ago has prompted some Democrats to call for a much harder line and to shut down the Senate by effectively grinding business to a halt. But party leaders don’t think that will work.

“I’ve been around here a few years,” Durbin said. “You can slow things down, but you can’t stop them. And there comes a point when we would use whatever tools we have available. But ultimately there will be a vote.”

CNN’s Rebecca Grandahl, Daniella Mora, Ali Zaslav, Austen Bundy and Dominic Torres contributed to this story.