Like the rest of her colleagues in Congress, Democrat Mikie Sherrill doesn't have a transcript of President Donald Trump's phone call with Ukraine's president.

But based on what she knows and what Trump has said himself about it, Sherrill, a former federal prosecutor, said she believes the president "crossed the line" — and committed acts that could warrant his impeachment.

"If I had somebody up on a wire saying the things the president has said, I would consider some of them threatening,'' Sherrill said in an interview Tuesday with the USA TODAY NETWORK New Jersey. And in a statement she said Trump may have tried to "fix" the 2020 election.

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In some ways, it's remarkable to hear Sherrill talk this way. She studiously avoided uttering the I-word, choosing instead to cast herself as a conventional "district first" servant from Montclair, focusing on bread-and-butter issues: expanding health care, building a new train tunnel to New York City and gun control.

But Sherrill, a former U.S. Navy helicopter pilot, went from fence-sitter to front-line advocate when she co-authored an op-ed published in the Washington Post on Monday, with six other House freshmen who have military and national security backgrounds, urging the House to impeach Trump if allegations of his interactions with the Ukrainian leader are proved true.

The cautious Sherrill didn't take the full plunge into the pro-impeachment camp that others on the left have taken — she still referred Tuesday to impeachment as a "tool" to be wielded if the facts line up, or possibly to compel Trump to cooperate with House investigations.

But her decision to suddenly seize the bully pulpit with her colleagues created a sense that the dam had burst, forcing a reluctant House Speaker Nancy Pelosi to launch a formal impeachment inquiry Tuesday.

By citing their past careers "in the defense of our country,'' Sherrill and her colleagues framed their statement as rooted in self-sacrifice and principle, not partisanship.

"This is something that implicates our ability to defend our democracy, and I think people are paying attention and this is a pretty clear case,'' Sherrill said.

Trump is alleged to have pressured the Ukrainian president to launch a corruption investigation of Hunter Biden, the son of former Vice President Joe Biden, a leading contender for the 2020 presidential nomination.

Trump reportedly withheld payment of nearly $400 million in arms shipment and other aid to Ukraine. The allegations are said to be contained in a whistle-blower complaint that the Trump administration is refusing to provide to Congress.

Trump has dismissed the allegations as another Democratic witch hunt, and to head off the firestorm, he vowed Tuesday to release a “complete, fully declassified and unredacted” transcript of his disputed phone call with Ukrainian President Volodymyr Zelensky.

Yet those moves are unlikely to quell Democratic fury and questions about whether Trump's decision to withhold the aid was a lever to prod Ukraine to dig up dirt that could help Trump undercut a competitor for the presidency.

"I don’t think we should be too quick to say that we don’t have hard evidence. We have evidence that he withheld arms shipments,'' Sherrill said. "The president said himself that he tried to make the case for corruption against the Bidens, with Ukraine’s president. ... I do think we have some evidence that gives me some grave concerns about how this president is conducting himself."

Sherrill said she didn't feel that the Democrats "made the case to the American people" for impeachment — until now. She said of Trump's alleged conduct, if proved true,

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Her shift to the pro-impeachment camp comes at a time when grassroots activists — who helped Sherrill seize a Republican redoubt in the wealthy North Jersey suburbs in last year's midterms — have been calling for Trump's impeachment. She is likely to face a primary challenge from Mark Washburne, a County College of Morris professor, who has been critical of her cautious stance on impeachment. Washburne placed a distant third in the 2018 primary against Sherrill.

And a survey this summer by the group NJ 11th for Change found that 77 percent of its members felt there was enough evidence to impeach Trump, although 62 percent supported moving ahead with proceedings, said Saily Avelenda, the group's executive director.

Avelenda said she was not surprised by Sherrill's decision, even though her caution may have confounded some of her fellow activists.

"This was exactly the trigger she would need to change her mind, because it had a very clear national and international security angle,'' she said. "And if you followed her for ... three years, you know that this would be her trigger."

Sherrill brushed aside suggestions that by citing impeachment as an option, she was giving herself some wiggle room in case the wily Trump finds a way out of this firestorm and Democrats are left with egg on their faces.

"I don’t think it's hedging in any way. I simply think we’ll see which tools we’ll need,'' she said. "I’m happy to explore any or all options for how we get to the bottom of this."