WASHINGTON — Representative Katie Porter, a law professor who narrowly flipped part of Republicans’ Southern California stronghold to the Democrats in last year’s midterm elections, said on Monday that she would support opening an impeachment inquiry into President Trump.
The announcement makes Ms. Porter one of the first to endorse impeachment of the 40 or so “front-line Democrats” whose seats are deemed endangered by their party. It could signal a more complex challenge ahead for Speaker Nancy Pelosi as she tries to navigate the thorny politics of resisting impeachment proceedings, demonstrating that support for such a move is no longer limited to lawmakers from the party’s safest districts.
In a video posted Monday evening announcing her decision, Ms. Porter, 45, nodded to the political strain of her position. But she argued that Mr. Trump’s refusal to comply with congressional investigations after the report by Robert S. Mueller III, the special counsel, had brought the country to “a crisis” she had not imagined as she campaigned last fall focused on pocketbook issues like health care and housing.
“The administration has refused to respect the rule of law. They have ignored multiple subpoenas; they’ve directed current and former high-ranking officials to disregard summons to testify; and the president has continued his efforts to spread mistrust of our law enforcement, contempt for our journalists, and false information about the law, Director Mueller’s findings, and basic, uncontested facts,” Ms. Porter said. “The question is not whether a crisis is in our midst, but rather whether we choose to fight against it.”
The number of House Democrats favoring at least opening an impeachment inquiry now numbers above 60, roughly a fourth of the caucus. Two more liberal Democrats added their names to the impeachment rolls in recent days, as well: Representatives Dan Kildee of Michigan and Carolyn B. Maloney of New York, whose Manhattan district runs alongside that of Representative Jerrold Nadler, the Judiciary Committee chairman.
But so far, only one other freshman Democrat representing a swing district, Representative Tom Malinowski of New Jersey, has endorsed the idea. Representative Harley Rouda of California, whose Orange County district sits near Ms. Porter’s, has said that if the Trump administration does not end its blockade of congressional subpoenas by the end of June, he will follow suit.
It is unclear whether the announcement by Ms. Porter — who defeated Mimi Walters, a Republican, by four percentage points — will persuade other endangered Democrats to follow course. The decision almost instantly opened her to attacks by Republicans eyeing a comeback in Orange County, something Democratic leaders have feared if the party pursues a partisan impeachment. Torunn Sinclair, a spokeswoman for House Republicans’ campaign arm, said Ms. Porter was thumbing “her nose at her constituents” and the decision would “cost Porter her seat in Congress in 2020.”
Despite near constant provocations from Mr. Trump, the majority of centrist lawmakers, many of whom have to run in districts Mr. Trump won in 2016, continue to oppose impeachment, preferring the slower approach advocated by Ms. Pelosi.
The speaker has been on a campaign to make the case against impeachment, saying in private and public that the move is the most divisive that Democrats could pursue. Instead, she has hammered away at a three-pronged strategy for challenging Mr. Trump — “legislate, investigate, litigate”— by pressing forward with measures to check his power and secure elections, scrutinizing his conduct and his administration’s policies, and taking legal action to compel his inner circle to answer to Congress.
But as she has brushed off suggestions she is taking heat within her own party, Ms. Pelosi has sharpened her own messaging against Mr. Trump, almost in direct proportion to the fervor within her ranks for impeaching him, telling reporters that he does not know right from wrong and “is involved in a criminal conspiracy.”
People close to the speaker likened her effort to the one she undertook during the midterm elections, when she resisted calls to make the races about Mr. Trump and instead encouraged Democrats to keep a single-minded focus on health care and other issues that polls showed were overwhelmingly popular with voters.
Representative Katie Hill, another freshman from a competitive district in California, said she was comfortable holding off on impeachment for now, but she has been spending more time educating people about the process.
“We’re getting more and more calls for impeachment, but when I explain it to people about these are the steps that we’re taking for accountability, then people understand,” Ms. Hill said last week in an interview. “They mainly want to know that we’re making forward movement. Many people are in a similar boat as I am, where if he takes it another step — if he defies a court order, or if and when we find evidence of underlying crimes — then we’re going to have to reassess.”
For her part, Ms. Porter acknowledged that she campaigned for office on lowering prescription drug costs, addressing the lack of affordable housing in Orange County and other policy issues — not impeaching Mr. Trump, despite his relatively weak support there. She framed her decision, though, as consistent with the values she presented to voters.
“When faced with a crisis of this magnitude, I cannot with a clean conscience ignore my duty to defend the Constitution,” Ms. Porter said in the video. “I can’t claim to be committed to rooting out corruption and putting people over politics and then not apply those same principles and standards in all of the work I do.”