Two Obama administration officials will testify in an open hearing before the House Intelligence Committee as part of ongoing investigations into Russian meddling in the 2016 presidential election.The U.S. intelligence community has concluded that Russia attempted to help Donald Trump win the election. Investigations by the House, Senate and FBI are examining what exactly Russia did and whether the Trump campaign was involved, among other questions.Former acting Attorney General Sally Yates and former Director of National Intelligence James Clapper are scheduled to appear before the House committee on May 8.It's a long-delayed hearing. Yates and Clapper, along with former CIA Director John Brennan, were originally scheduled to testify in late March, but those plans were scuttled amid a simmering soap opera of distrust and missteps within the House committee.Yates, specifically, was at the center of one portion of the drama: Multiple sources accused the White House of attempting to block her from testifying.Rep. Adam Schiff, the ranking Democrat on the House committee, told NPR that the Trump administration worked behind the scenes to stop Yates' testimony. He said White House officials were worried about what she'd reveal about the administration's response when Yates told them about the investigation into Michael Flynn. (Flynn briefly served as national security adviser, resigning after it was revealed he'd concealed his contacts with the Russian ambassador.)The Washington Post also reported that the White House tried to block Yates from testifying. The newspaper published letters exchanged by the Justice Department and Yates' lawyer, in which the Justice Department says Yates' communications are "likely" covered by executive privilege, which would mean it is up to the president whether they are disclosed.The Trump administration has denied putting pressure on the House investigation and called the Post story "entirely false."Yates and Clapper aren't the only high-profile witnesses appearing before the investigation.FBI Director James Comey and National Security Adviser Mike Rogers — who already testified at an open hearing last month — will also appear before the committee in a closed hearing on May 2.A number of Trump campaign members, including Roger Stone, Carter Page and Paul Manafort, have volunteered to give testimony. Flynn has suggested he will testify if he's given immunity from prosecution. All those men have been under scrutiny over ties to Russia.As part of the investigation into Russian meddling, Republicans on the House committee are also extremely interested in a different set of issues: who leaked classified information about ties between the Trump team and Russia, who requested that names of Trump associates be "unmasked" and whether intelligence was abused for political purposes.Some Republicans on the committee are likely to pursue that line of questioning during the testimony of the Obama administration officials.Meanwhile, there are reports, citing anonymous sources, that the Senate Intelligence Committee's parallel investigation into Russian meddling efforts is stagnating.The Senate investigation, unlike the House investigation, is taking place almost entirely behind closed doors.Tim Mak of The Daily Beast reports that there are no full-time staff members working on the Senate inquiry and that "no interviews have been conducted with key individuals."And Michael Isikoff of Yahoo News reports that the committee "has yet to issue a single subpoena for documents," in addition to failing to interview any central witnesses. Copyright 2017 NPR. To see more, visit http://www.npr.org/.