A coalition of national security Democrats, including five freshmen with military experience, on Tuesday blasted President Donald Trump’s alleged political dealings with Ukraine as a potential “impeachable offense” and joined their House colleagues in demanding the White House provide public answers on the scandal.

In a Washington Post opinion piece Monday night, the group — all of whom represent districts Democrats flipped in the last mid-term election — called the latest accusations stunning and a significant national security threat.

Trump on Sunday seemed to acknowledged that, during a recent phone conversation, he urged Ukrainian President Volodymyr Zelensky to look into links between corruption in that country and Hunter Biden, the son of former vice president and current Democratic presidential hopeful Joe Biden.

Trump later backtracked on those comments and denied charges that he withheld U.S. foreign aid to Ukraine to pressure that government into investigate the Bidens. The issue is the focus of an ongoing whistleblower complaint against the president, who has blasted the entire controversy as a political smear campaign.

“The president of the United States may have used his position to pressure a foreign country into investigating a political opponent, and he sought to use U.S. taxpayer dollars as leverage to do it,” the Monday night op-ed stated.

“He allegedly sought to use the very security assistance dollars appropriated by Congress to create stability in the world, to help root out corruption and to protect our national security interests, for his own personal gain … If these allegations are true, we believe these actions represent an impeachable offense.”

The opinion piece was authored by Reps. Elanie Lauria of Virginia, Mikie Sherrill of New Jersey, Chrissy Houlahan of Pennsylvania, Gil Cisneros of California and Jason Crow of Colorado, all of whom served in the military.

Reps. Abigail Spanberger of Virginia, who served in the Central Intelligence Agency, and Elissa Slotkin of Michigan, who worked in the CIA and Defense Department as a civilian, also signed on to the piece.

“Everything we do harks back to our oaths to defend the country,” the group wrote. “These new allegations are a threat to all we have sworn to protect. We must preserve the checks and balances envisioned by the Founders and restore the trust of the American people in our government.”

A majority of House Democrats have publicly stated support for starting impeachment hearings, but the addition of the new group of moderate Democrats adds new focus on the effort.

Most Republicans in Congress thus far have remained quiet on the issue or attacked Democrats for fabricating charges against the president. On Monday, Senate Majority Leader Mitch McConnell, R-Ky., accused the other party of moving too quickly to attack Trump without any evidence.

“I believe it's extremely important that (this investigation) be handled in a secure setting with adequate protections in a bipartisan fashion and based on facts rather than leaks to the press,” he said.

“It is regrettable that (top Democrats) have chosen to politicize the issue, circumventing the established procedures and protocols that exist so the committees can pursue sensitive matters in the appropriate, deliberate bipartisan manner.”

House Democratic leaders are expected to hold meetings with members on the issue later Tuesday.