Democrats on the House Intelligence Committee asked Mr. Murphy to testify in private on Sept. 21, a possible precursor to a public hearing in the weeks before Election Day.
“We will get to the bottom of this, expose any and all misconduct or corruption to the American people, and put a stop to the politicization of intelligence,” said Representative Adam B. Schiff, Democrat of California and the chairman of the committee. He said the allegations of politically censored intelligence assessments were particularly worrisome in light of the Trump administration’s decision last month to stop briefing lawmakers in person on election security threats.
Sarah Matthews, a White House spokeswoman, said in a statement that Mr. O’Brien had “never sought to dictate the intelligence community’s focus on threats to the integrity of our elections or on any other topic.” She called Mr. Murphy a “disgruntled former employee” whom Mr. O’Brien had never heard of. But, she added, the national security adviser “consistently and publicly advocated for a holistic focus on all threats to our elections — whether from Russia, Iran, China or any other malign actor.”
Alexei Woltornist, the spokesman for the Homeland Security Department, rejected Mr. Murphy’s allegations.
“We flatly deny that there is any truth to the merits of Mr. Murphy’s claim,” Mr. Woltornist said. “D.H.S. looks forward to the results of any resulting investigation, and we expect it will conclude that no retaliatory action was taken against Mr. Murphy.”
As a senior analyst and then the top intelligence official at the Homeland Security Department, Mr. Murphy was responsible for producing regular updates for the F.B.I., state election authorities and law enforcement on threats to U.S. elections by foreign powers.
In May, he said, Mr. Wolf directed him to stop providing assessments of the Russian threat, which favored Mr. Trump’s re-election, and instead focus on the activities of China and Iran, two other states that intelligence analysts have said pose a possible threat to the election and oppose Mr. Trump. China and Iran have so far not taken the kind of active measures that Moscow has, intelligence analysts say.