Two hundred and eighteen House Democrats and one independent — a majority of the chamber's 435 members — now favor some kind of impeachment action against President Donald Trump, according to an NBC News tally.

House Democrats reached the milestone a day after Speaker Nancy Pelosi announced a formal impeachment inquiry into the president following claims that he might have withheld aid to Ukraine to pressure officials there to investigate former Vice President Joe Biden and his son.

That nearly all House Democrats support some kind of impeachment action represents a significant development in the chamber's push forward with official impeachment proceedings.

But that doesn't mean they will all vote to impeach the president.

Some House Democrats, as well as Rep. Justin Amash, I-Mich., have asked for an impeachment inquiry to examine any evidence of wrongdoing, while others have favored the House Judiciary Committee investigation. Still others have called for drafting articles of impeachment against Trump. The different terms the lawmakers are using to discuss the issue make it unclear how they will vote if articles of impeachment were to go before the full House. The Democratic holdouts, meanwhile, include several of those in competitive districts — some who flipped seats last year.

Until recently, less than half of the 235-member Democratic Caucus said they favored taking impeachment action against the president, and Pelosi had tamped down efforts to launch a formal impeachment push, dismissing it as too divisive.

But the number of Democrats backing formal impeachment measures spiked in the weeks after special counsel Robert Mueller's July testimony to the House Judiciary and Intelligence committees about his probe into Trump and Russia, and it snowballed in the past several days amid revelations about a phone call Trump held in July with Ukrainian President Volodymyr Zelenskiy, in which they discussed the Bidens.

On the call, Trump asked Zelenskiy to investigate the 2020 Democratic presidential candidate and his son, Hunter, who had business dealings in Ukraine. Just days before the conversation, Trump had instructed his chief of staff to place a hold on about $400 million in military aid to the country, which is involved in a continuing military conflict with Russia, which The Washington Post and other news outlets reported earlier this week and NBC News confirmed.

A description of the call made public Wednesday by the Trump administration shows Trump asking the Ukrainian president to look into why that country's top prosecutor apparently had ended an investigation of the business dealings of Biden's son, who served on the board of a Ukrainian gas company, and alleging that the then-vice president "went around bragging that he stopped the prosecution, so if you can look into it. ... It sounds horrible to me."

The text record of the call, which the White House said was not verbatim but represented "notes and recollections" of Situation Room and National Security Council staff who listen to the conversation, is reportedly at the center of a whistleblower complaint from U.S. intelligence community member. The intelligence community's inspector general deemed the complaint an "urgent concern" that he was required by law to provide to the congressional intelligence committees, but the Trump administration blocked the move, resulting in a standoff with Congress and drawing a warning from Pelosi about "a whole new stage of investigation" if the complaint weren't released. NBC News has not independently confirmed that Ukraine is at the center of the whistleblower issue.