The investigation was revealed in letters that the committee’s Democratic leaders sent Wednesday to Kemp and his successor as secretary of state, Brad Raffensperger. The letters instructed Kemp and Raffensperger — both Republicans — to provide by March 20 a wide range of documents concerning voter roll purges; holds placed on voter registration applications; polling site changes and closings; and other voting-related issues.

The committee also requested all documents related to the potential conflict of interest Kemp faced in administering an election in which he was a candidate.

“The Committee is particularly concerned by reports that Georgians faced unprecedented challenges with registering to vote and significant barriers to casting their votes during your tenure as secretary of state and during the 2018 election,” Reps. Elijah E. Cummings, the committee chairman, and Jamie Raskin, head of the Subcommittee on Civil Rights and Civil Liberties, wrote to Kemp.

Kemp and Republicans on the committee immediately dismissed the investigation as a political effort, aimed at undermining the results of an election that Democrats lost.

The letter outlined several points of scrutiny during the 2018 governor’s race, in which Stacey Abrams, a Democrat, posed a strong challenge to Kemp in a normally solidly Republican state.

Many voters, especially in heavily African-American counties, waited at polling places for hours while “hundreds of available voting machines sat unused in government warehouses,” the letter noted. State officials had sequestered those machines in response to a federal lawsuit that said they were vulnerable to hacking.

Tens of thousands of voter registration applications, mostly from African-Americans, were held up under a state law that requires the name on the application to exactly match the name on the applicant’s government ID; even a missing hyphen can cause problems.

Kemp’s office purged more than 1.4 million voters from the rolls during his tenure. (States are required to keep their rolls up-to-date and remove people who have moved, but some, including Georgia, have been much more zealous than others, starting the purging process on the basis of a voter not having cast a ballot recently.) And county and state officials closed more than 200 polling places from 2012 to 2018.

Throughout the campaign, Kemp denied intentional voter suppression. Asked for comment Wednesday, his spokesman directed The Times to video of a news conference where Kemp suggested that the investigation was a politically motivated distraction from more important issues.

“They need to quit playing politics up there,” Kemp said at the news conference, before pivoting to an attack on House Democrats for giving billions of dollars in disaster aid to Puerto Rico “when we have our own farmers that are fixing to lose their farm.” He said nothing about the substance of the allegations or the document requests, and his spokesman did not respond to a follow-up email.

Raffensperger, the current secretary of state, said that he had received his own letter and that his office “looks forward to an open dialogue and a thorough process.”

Cummings and Raskin, the Democratic committee leaders, were not immediately available for interviews Wednesday. But their decision to open the investigation was more evidence that House Democrats, newly empowered by the November election, intend to act aggressively on issues like allegations of voter suppression that were on the back burner for the first two years of the Trump administration.

Rep. Jim Jordan, the committee’s ranking Republican, said through a spokesman that it was “highly unusual for a congressional committee to involve itself in a state’s election.”

“This is squarely in the purview of the state of Georgia, not the House Oversight Committee,” Jordan said in a statement. “We can’t help but think that attempts by the Democrats to insert the committee into the state’s business is an attempt to relitigate an election result that they do not like."

Kemp narrowly defeated Abrams, who ended her campaign by declaring, “This is not a speech of concession, because concession means to acknowledge an action is right, true or proper.”

This article originally appeared in The New York Times.