Some Democratic lawmakers who have been reluctant to push for an impeachment inquiry of President Donald Trump appeared to warm to the idea after Trump admitted to a July conversation with his Ukrainian counterpart about investigating a company linked to the son of Joe Biden.

House Intelligence Chairman Adam Schiff of California suggested Sunday that the House may have “crossed the Rubicon” as new revelations about Trump’s conversation with Ukrainian president Volodymyr Zelensky emerged in media reports. Until now leadership in the Democrat-controlled House has been ambiguous about whether it is pursuing an impeachment investigation against the president.

“I have been very reluctant to go down the path of impeachment,” Schiff said in an interview on CNN. “But if the president is essentially withholding military aid at the same time he is trying to browbeat a foreign leader into doing something illicit, providing dirt on his opponent during a presidential campaign, then that may be the only remedy that is coequal to the evil that that conduct represents.”

Trump on Monday acknowledged that he talked to Ukraine’s Zelensky, a former comedian-turned-politician, about that country’s government investigating the involvement Biden’s son with a Ukrainian energy company.

The president initially suggested Monday that reports he was dangling a $250 million military aid package to the country in exchange for an investigation had merit. Ukraine is fighting Russian-backed separatists in its eastern region.

“It’s very important to talk about corruption. If you don’t talk about corruption, why would you give money to a country that you think is corrupt?” he told reporters at a UN General Assembly meeting in New York, appearing to confirm he wanted to trade a probe for an aid package to Ukraine. “It’s very important that on occasion you speak to somebody about corruption.”

But later Monday, Trump flatly denied holding up the U.S. aid package in exchange for a promise for an investigation into the Bidens. “I did not make a statement that you have to do this or I won’t give you aid,” he told reporters.

Schiff has been the Democrats’ point man in their efforts to obtain a whistleblower complaint regarding the call.

The White House and acting Director of National Intelligence Joseph Maguire have blocked the release of the complaint to Congress. That has allowed the president and his lawyer, Rudy Giuliani, to try shape a narrative about the circumstances surrounding the call, which Trump has said others were listening to.

Giuliani has freely admitted he had multiple conversations with Ukrainian officials about his contention that while Biden was vice president, he convinced the Ukrainian government to drop an investigation into a company linked to one of Biden’s sons. Giuliani claimed on CNN last Thursday that there was nothing inappropriate about his conversations with Ukrainian officials.

Revelations about the whistleblower complaint have reignited the pleas of vocal progressives in the Democratic caucus who have for months pressured the party brass to more officially and vigorously pursue impeachment.

“At this point, the bigger national scandal isn’t the president’s lawbreaking behavior — it is the Democratic Party’s refusal to impeach him for it,” Rep. Alexandria Ocasio-Corteztweeted on Saturday.

“The integrity of our democracy isn’t threatened when a president breaks the law. It’s threatened when we do nothing about it,” the freshman New York Democrat wrote.

Some moderate Democrats who have resisted calls for impeachment so far appeared to be changing their tone on the matter as reports about the whistleblower complaint continued to emerge over the weekend.

“I don’t want to do any more to contribute to the divisiveness in the country but my biggest responsibility as an elected official is to protect our national security and Constitution,” Rep. Debbie Dingell of Michigan told The New York Times on Sunday.

Speaker Nancy Pelosi, who has staunchly opposed impeachment chatter to help provide cover for swing-district moderates in her caucus, did not directly mention impeachment in a dear-colleague letter to her caucus on Sunday.

But she did indicate that a “whole new stage of investigation” could be forthcoming if the Trump administration continues to stonewall congressional access to the whistleblower complaint.

Maguire is scheduled to appear before the House Intelligence panel on Thursday —Pelosi’s deadline for him to provide the whistleblower complaint to Congress.

Republican lawmakers’ response to the reports surrounding the whistleblower complaint has largely been mute, though some individuals have expressed concern about the contents.

“No president should ever utilize or use American power in any way like to affect an election,” said House Foreign Affairs Committee member Adam Kinzinger, an Illinois Republican. “So, if that happened, that would be a problem.”

“It’s one thing to go after corruption. We should. That’s a huge problem in Ukraine,” Kinzinger said Friday on CNN. “That’s a huge problem in Ukraine. But if you say, ‘Go after it specifically for a political target that affects somebody in office in the United States,’ that’s a major problem.”

Former Republican presidential nominee and Utah Sen. Mitt Romney tweeted Sunday that it was “critical” for the facts to emerge about Trump’s call with Ukraine, though he stopped short of laying out any tangible consequences the president might face.

“If the president asked or pressured Ukraine’s president to investigate his political rival, either directly or through his personal attorney, it would be troubling in the extreme,” Romney wrote.

Senate Judiciary Chairman Lindsey Grahamcalled for transparency from the Trump administration on Monday, even though he claimed Trump did not owe Congress information about the call because it is protected by executive privilege.

“Get ready for some disclosures from the president that I think will exceed every expectation,” the South Carolina Republican told conservative talk radio host Hugh Hewitt. “I can’t promise you this will happen, but I think the president will clear the air when it comes to the whistleblower allegation.”

John Bennett contributed to this report.