Updated at 4:50 p.m.: Revised to include comment from Trump campaign.

WASHINGTON — House Speaker Nancy Pelosi ended months of caution on impeachment Tuesday, launching a formal inquiry aimed at removing President Donald Trump over allegations he withheld aid from Ukraine to pressure that country to launch a corruption investigation into former Vice President Joe Biden.

"The president must be held accountable," she said in a six-minute speech, flanked by six American flags outside her office at the Capitol. "No one is above the law."

All 13 Texas Democrats in Congress also now support impeachment, or are at least open to it, after six holdouts in the delegation joined the chorus in the hours before her announcement — some more enthusiastic about the cause than others.

That shift came as Democrats around the country lined up to demand that impeachment proceedings begin, projecting a sense of unity and momentum amid rock-solid opposition from congressional Republicans in Texas and beyond and fierce push back from Trump himself.

Among the new Texas converts, the most explicit call came from Fort Worth Rep. Marc Veasey, who said he's ready to vote for impeachment immediately.

"No one is above the law — not even the occupant of the highest office — and that is why I support moving forward with an impeachment inquiry," he said.

Five others — Dallas Reps. Eddie Bernice Johnson and Colin Allred, Laredo Rep. Henry Cuellar, Houston Rep. Lizzie Fletcher and McAllen Rep. Vicente Gonzalez — said for the first time that they're ready to begin proceedings if the White House refuses to turn over a whistleblower complaint alleging misdeeds by Trump in his dealings with Ukraine, or as other evidence emerges against him.

"If the decision is made by the president and his administration to withhold this information from Congress, or if the allegations of his abuse of power are substantiated, I will be placed in a position where I must fulfill my constitutional duty and support impeachment proceedings," said Johnson, dean of the Texas congressional delegation and chair of the House science committee.

The newfound impeachment fervor followed last week's revelation about a July phone call between Trump and Ukraine's president — the importance of which Trump has downplayed.

Trump accused the Democrats of pursuing a "total witch hunt." His campaign manager, Brad Parscale, added that the "misguided Democrat impeachment strategy is meant to appease their rabid, extreme, leftist base, but will only serve to embolden and energize President Trump's supporters."

"Democrats can't beat President Trump on his policies or his stellar record of accomplishment, so they're trying to turn a Joe Biden scandal into a Trump problem," Parscale said.

But Trump has also acknowledged pressuring his Ukrainian counterpart to investigate Biden, the Democratic presidential front-runner, over the former vice president's son's business dealings in the country. And Pelosi said Trump's actions amounted to a "breach of his constitutional responsibilities."

"The actions of the Trump presidency revealed dishonorable facts of the president's betrayal of his oath of office, betrayal of our national security, and betrayal of the integrity of our elections," the San Francisco Democrat said, taking no questions from reporters after her announcement.

Pelosi directed the House Judiciary Committee to continue its work building an impeachment case against Trump. If the Democrat-run House ultimately votes to impeach Trump, then the GOP-run Senate would hold a trial on whether to convict the president.

The speaker's decision summed up a day in which long-simmering outrage among Democrats boiled over into an outburst of pro-impeachment enthusiasm. By early Tuesday afternoon, there was just one holdout among the 13 Texas Democrats in the House.

Cuellar, a centrist with the most GOP-friendly voting record of any House Democrat, initially preached patience, offering a statement that indicated impeachment would be premature. He said that although he was "concerned about the current allegations," he wanted to let congressional committees "continue their investigations to see if these allegations are true before we proceed with impeachment."

A primary challenger from the left, Jessica Cisneros, then hit him for being soft on impeachment, asserting that Cuellar would "rather toe the Trump line than take a stand for our country and this community."

Cuellar subsequently issued a statement in which he expressed for the first time a clear willingness to impeach Trump, putting him in line with other Texas Democrats: "No one is above the law, and if investigations prove that impeachment is the necessary course of action, then I will be forced to act on impeachment proceedings."

Other Democrats faced backlash from the right, leaving no doubt that Republicans in Texas and beyond remain united against impeachment.

"It's nothing but naked politics," said Texas Sen. John Cornyn, a Republican, dismissing the renewed focus on impeachment.

The GOP paid particular attention to Democrats representing swing districts. Allred last year toppled longtime congressman Pete Sessions in the midterm elections that saw Democrats take back the House from the GOP. Fletcher, meanwhile, took out another senior Republican: Rep. John Culberson.

Fletcher stopped short of saying the time for impeachment is already ripe. Allred said that Trump must comply with federal law and turn over the whistleblower complaint to Congress by Thursday.

"If he does not, and this administration continues to violate the law and obstruct Congress' constitutional duty, I will be forced to conclude that the only remaining option is for the House to begin impeachment proceedings," Allred said.

Republicans ripped into both freshman lawmakers.

"Maybe Allred should tone down the tough-guy act and try listening to his constituents for a change," said Bob Salera, spokesman for the National Republican Congressional Committee, asserting that impeachment remains "grossly unpopular."

The Trump Victory Committee, a joint effort of the GOP and the Trump campaign, accused Fletcher of siding with the "far-left, anti-President Trump socialist squad."

"Lizzie Fletcher has put her constituents on the backburner and her personal ambitions at the center of her disastrous platforms," said spokeswoman Samantha Cotten.

1 / 3President Donald Trump speaks during the 74th Session of the United Nations General Assembly at UN Headquarters in New York on Sept. 24, 2019.(TIMOTHY A. CLARY / Getty Images) 2 / 3Rep. Eddie Bernice Johnson, D-Dallas, bows her head as she thanks supporters for voting for her as she makes remarks during state Sen. Royce West's campaign launch for U.S. Senate at the CWA Local 6215 Union Hall in Dallas on July 22, 2019.(Shaban Athuman / Staff Photographer) 3 / 3Rep. Henry Cuellar, D-Laredo, delivers remarks during a rally for the passage of the USMCA trade agreement, on September 12, 2019 in Washington. Several agricultural groups including the American Farm Bureau Federation, the American Soybean Association and the National Corn Growers Association held the rally to urge Congress to ratify the deal.(Tom Brenner / Getty Images)

Freshman Rep. Lance Gooden, a Terrell Republican, went even further on Tuesday, demanding the ouster of House Judiciary Chairman Jerry Nadler and accusing him of pursuing an impeachment inquiry without a mandate from the House.

Even before the furor over Trump's Ukraine call, seven Texas lawmakers, all Democrats, had backed at least opening an impeachment inquiry, according to a tracker maintained by Politico: Reps. Al Green, Sheila Jackson Lee and Sylvia Garcia of Houston, Rep. Joaquin Castro of San Antonio, Rep. Filemon Vela of Brownsville, Rep. Veronica Escobar of El Paso and Rep. Lloyd Doggett of Austin.

Green has demanded Trump's impeachment from the outset of his presidency and has managed to bring impeachment resolutions to the floor three times, starting in December 2017.

The rest of the Texas Democratic delegation started falling in line on Monday night. Gonzalez, the McAllen Democrat, appeared on CNN to say that if Trump withheld military aid to Ukraine in exchange for a reopening of an investigation into Biden's son, he would also support an impeachment inquiry.

"I don't think we have a choice under the Constitution," he said. "We must move forward with impeachment proceedings. I don't think we'll have much of a choice."

Others followed suit on Tuesday, each offering their own caveats. Fletcher, for instance, was more cautious.

She called Trump's actions "a gross abuse of power and an abuse of the trust we the people have placed in the Office of the President." She demanded the administration cooperate fully with congressional inquiries and said that "the House of Representatives should act swiftly to investigate and should be prepared to use the remedy exclusively in its power: impeachment."

Trump, meanwhile, has insisted that he never threatened Ukraine and that his pressure for a corruption inquiry into Biden's son was not part of a quid pro quo.

But major news outlets reported late Monday that the timing of the call left little doubt for Ukraine about the consequences of refusal. Only days before his call with Ukraine's president — in which Trump has acknowledged demanding the corruption inquiry — Trump had frozen $391 million in aid.

He personally ordered acting chief of staff, Mick Mulvaney, to block the congressionally mandated funding for Ukraine, an order the White House budget office conveyed to the Pentagon and State Department with a vague explanation that the president had "concerns."

On Tuesday, Trump told reporters in New York, where he's attending the annual United Nations General Assembly, that he froze aid to Ukraine because he wanted Germany, France and other European allies to contribute more to the effort to help that country deter Russian aggression.

That contradicted Trump's claim from Sunday, when he said he froze the aid because of concerns about "corruption" in Ukraine.

On Tuesday afternoon he announced that he had ordered the release Wednesday of the full transcript of the phone call in question, insisting that it will show no pressure and nothing inappropriate, though critics note that by then, he had frozen hundreds of millions in aid, making the threat implicit.

....You will see it was a very friendly and totally appropriate call. No pressure and, unlike Joe Biden and his son, NO quid pro quo! This is nothing more than a continuation of the Greatest and most Destructive Witch Hunt of all time! — Donald J. Trump (@realDonaldTrump) September 24, 2019

Democrats declared that offering insufficient. The Democratic chairmen of the House intelligence, oversight and foreign affairs panels sent the White House a blistering letter on Tuesday demanding the administration turn over the whistleblower complaint itself.

But Cornyn called Democrats' allegations presumptuous.

"They don't know what was said on the call. They don't know what the facts are," he said in an interview, adding that clarity could come from upcoming congressional hearings with the acting director of national intelligence — the official who has refused to comply with a federal law requiring the intelligence community's inspector general to turn over to Congress a whistleblower complaint deemed urgent.

"I know people around here leap to a conclusion first and get the facts later," Cornyn said. "I'd prefer to do it the other way."