Rep. Katherine Clark Katherine Marlea ClarkDemocratic leaders: Supreme Court fight is about ObamaCare Rep. Robin Kelly enters race for Democratic caucus vice chair Clark rolls out endorsements in assistant Speaker race MORE (D-Mass.) on Thursday became the highest-ranking member of House Democratic leadership to endorse an impeachment inquiry a day after former special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's testimony before Congress.

Clark, the House Democratic Caucus vice chair, ranks sixth in the leadership hierarchy.

Like other Democrats who also have endorsed an impeachment inquiry, Clark said that it should be the path forward given the Trump administration's general refusal to cooperate with their investigations.

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"I deeply respect the committee work of House Democrats to hold the President accountable, including hearings, subpoenas and lawsuits. All of our efforts to put the facts before the American people, however, have been met with unprecedented stonewalling and obstruction," Clark said in a statement.

"That is why I believe we need to open an impeachment inquiry that will provide us a more formal way to fully uncover the facts."

But Clark also cited Mueller's congressional testimony, as well as Senate Republicans' efforts to block election security legislation in the hearings' aftermath.

"Revisiting the President’s obstruction of justice during the Special Counsel’s testimony was disturbing. However, the moment that truly stunned me was when Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellTrump 'no longer angry' at Romney because of Supreme Court stance On The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline The Hill's Campaign Report: Trump faces backlash after not committing to peaceful transition of power MORE blocked a vote on an election security bill the same day Mr. Mueller warned that Russia interfered in our elections and is continuing to do so," Clark said.

Speaker Nancy Pelosi Nancy PelosiPelosi slams Trump executive order on pre-existing conditions: It 'isn't worth the paper it's signed on' On The Money: Anxious Democrats push for vote on COVID-19 aid | Pelosi, Mnuchin ready to restart talks | Weekly jobless claims increase | Senate treads close to shutdown deadline Trump signs largely symbolic pre-existing conditions order amid lawsuit MORE (D-Calif.) has long said that a case for an impeachment effort should be strong enough to draw bipartisan support.

Clark suggested that convincing Senate Republicans to come on board is unlikely but argued Democrats should move forward nonetheless.

"An impeachment inquiry is a process, not an outcome, but I fear there is no amount of wrongdoing that we could uncover that would convince Senate Republicans to hold the President accountable. Regardless of the outcome, I believe we have a patriotic duty to uncover the facts for the American people and uphold the rule of law," Clark said.

Clark is the fourth House Democrat to announce support for an impeachment inquiry since Mueller's marathon testimony on Wednesday, following Reps. Lori Trahan Lori A. TrahanEthics panel finds Massachusetts Democrat didn't violate rules Democrats on House Armed Services panel 'dismayed and gravely concerned' with Esper The Hill's Coronavirus Report: Pfizer's Mikael Dolsten says vaccine development timeline being cut in half; House poised to pass 4 billion relief package MORE (Mass.), Peter DeFazio Peter Anthony DeFazioAnxious Democrats amp up pressure for vote on COVID-19 aid Airline CEOs, union leaders implore Congress and the administration to avoid Oct. 1 furloughs Airline CEOs plead with Washington as layoffs loom MORE (Ore.) and Lisa Blunt Rochester (Del.).

A handful of other lower-ranking members of leadership have also called for an impeachment inquiry, including Rep. David Cicilline David Nicola CicillineClark rolls out endorsements in assistant Speaker race Races heat up for House leadership posts The folly of Cicilline's 'Glass-Steagall for Tech' MORE (D-R.I.), who runs Democrats’ messaging arm, and Reps. Barbara Lee Barbara Jean LeeOvernight Defense: Nearly 500 former national security officials formally back Biden | 40 groups call on House panel to investigate Pentagon's use of coronavirus funds 40 groups call on House panel to investigate Pentagon's use of coronavirus funds Overnight Defense: Pentagon redirects pandemic funding to defense contractors | US planning for full Afghanistan withdrawal by May | Anti-Trump GOP group puts ads in military papers MORE (D-Calif.), Ted Lieu Ted W. LieuThe spin on Woodward's tapes reveals the hypocrisy of Democrats Larry Kudlow defends response to coronavirus: Trump 'led wisely' Lieu on Trump 'playing it down' on coronavirus: 'This is reckless homicide' MORE (D-Calif.) and Jamie Raskin Jamin (Jamie) Ben RaskinOVERNIGHT ENERGY: House passes sweeping clean energy bill | Pebble Mine CEO resigns over secretly recorded comments about government officials | Corporations roll out climate goals amid growing pressure to deliver On The Money: House panel pulls Powell into partisan battles | New York considers hiking taxes on the rich | Treasury: Trump's payroll tax deferral won't hurt Social Security House panel pulls Powell into partisan battles over pandemic MORE (D-Md.).

The number of House Democrats supporting an impeachment is nearing 100, according to The Hill's whip list. But it's still less than half of the 235-member caucus.