WASHINGTON – The unexpected death Thursday of Rep. Elijah Cummings has meant the loss of a key Democratic leader, an eloquent voice for and confidante of House Speaker Nancy Pelosi who played a central figure in the House's ongoing impeachment inquiry into President Donald Trump.

Cummings, who served as chairman of the powerful House Oversight and Reform Committee, will be succeeded by New York Democrat Carolyn Maloney on an acting basis. And there's no indication that the inquiry, now in its fourth week, is slowing down amid the tragedy.

Pelosi said the House is continuing to gather evidence and talk to witnesses as it investigates efforts by Trump to pressure the Ukrainian government to provide potentially damaging information on 2020 political rival Joe Biden and his son, Hunter.

Trump's acting chief of staff acknowledged Thursday that financial aid to Ukraine at the center of a House impeachment inquiry was withheld because of the president's desire for the country to engage in U.S. politics.

Mick Mulvaney's assertion was the first time a White House official has conceded Trump set up a quid quo pro scenario in which money approved by Congress for Ukraine was used as leverage, though he defended the arrangement as standard practice.

The son of sharecroppers, Cummings was one the earliest and most aggressive committee chairmen investigating Trump, sending requests for information while in the minority during the first two years of the president's term and then calling hearings and demanding documents after Democrats regained control of the House in January.

He accused the administration of stonewalling his requests for documents on a variety of subjects including whether Trump was profiting unconstitutionally from his namesake business while president and why a citizenship question was proposed for the U.S. Census in 2020.

Here are some key questions about Cummings, Maloney and where the impeachment process goes from here:

Q: What was Cummings' role in helping lead impeachment efforts?

A: As chair of a committee responsible for unearthing evidence of potential corruption, the Maryland Democrat has been at the center of the impeachment effort by leading a panel that demanded key documents and records.

In recent weeks, Cummings' panel has issued several subpoenas to key witnesses in the investigation: Energy Secretary Rick Perry about his contacts with the Ukrainian government; to the lawyer for two Ukrainian-born business partners who helped Trump's personal lawyer, Rudy Giuliani, in trying to find dirt on the Bidens; and the White House itself for pertinent documents.

Latest witness:Impeachment inquiry: Trump ambassador 'disappointed' with Rudy Giuliani's influence in Ukraine policy

Even before the formal impeachment inquiry, Cummings was responsible for convening the committee hearing in February when Trump's former attorney, Michael Cohen, testified that the president encouraged him to lie to Congress and the public for Trump's protection.

Q: How will the loss of Cummings affect impeachment?

A: The West Baltimore native (who got into a very public spat about his hometown with the president earlier this summer) has been a forceful voice against the Trump administration on a number of issues including the cost of prescription drugs and civil rights.

Leading the Oversight and Reform Committee, Cummings was one of the three chairmen heading the impeachment (along with Intelligence Chairman Adam Schiff, D-Calif., and Foreign Affairs Eliot Engel). Cummings' death.

But Pelosi made clear that the inquiry was still on track despite a tragedy that silenced one of Congress' most powerful voices.

"The timeline (on impeachment) will depend on the truth line," Pelosi told reporters Thursday morning.

Q: Who is Carolyn Maloney, the congresswoman who will take over the House and Oversight Committee on an acting basis?

A: The former New York City teacher with a first-degree black belt in Taekwondo, Maloney has a reputation as a tenacious champion for women's rights and consumer protections over her nearly 14 terms in Congress.

Not necessary:Nancy Pelosi: No need for House to hold formal vote on impeachment inquiry already under way

She's also been a leader on issues tied to the Sept. 11 attacks, including the creation of the commission examining the terrorist attacks and efforts to compensate first responders who developed health problems following the disaster.

Maloney, 73, has also been a vocal supporter of Trump's impeachment, saying in September during a rally on Capitol Hill that Trump has committed "treason" by pressuring Ukraine to dig up dirt on political rival Joe Biden.

"We will get to the bottom of this," she said at the rally. "We will not let the president get away with breaking the law."

Q: What's next for the impeachment process?

A: Witnesses continue to be called in front of the committee.

Gordon Sondland, the U.S. ambassador to the European Union, was the latest witness, telling the House impeachment panel Thursday that he was disappointed that he had to consult with Giuliani on Ukraine policy and that withholding military aid for a political investigation would be "wrong."

Republicans had hoped to slow, or kill, the inquiry by forcing the House to hold a formal vote on whether to authorize the inquiry that Pelosi launched last month.

But the Speaker rejected such calls Tuesday, saying it was not necessary to take the additional step on a probe that is already well underway.

"There's no requirement that we have a vote," Pelosi said. "We're not here to call bluffs. We're here to find the truth to uphold the Constitution of the United States. This is not a game for us. This is deadly serious."

Trump has vowed not to cooperate with the inquiry unless the House holds a vote to officially launch it. Democrats, in turn, had considered holding such a vote, potentially in case the courts said such a move was necessary to compel administration officials and other potential witnesses in the investigation to provide documents and appear for testimony.