Jay Sekulow, in a file photo from October 2015, is a member of President Trump’s legal team. Some Trump supporters are urging a shake-up of the president’s legal advisers
The Russia investigation that Donald Trump’s legal team predicted would clear the president by year’s end looks to stretch into 2018, prompting his supporters to ratchet up complaints that Special Counsel Robert Mueller’s operation is politically motivated.
The calls for a more aggressive approach have intensified amid disclosures that a senior agent on Mr. Mueller’s team, Peter Strzok, had sent text messages that were allegedly critical of Mr. Trump during the 2016 election. Mr. Mueller subsequently removed Mr. Strzok from the probe.
Republicans also point to Andrew Weissmann —a Mueller deputy who had applauded the Justice Department’s decision not to defend the initial White House travel ban on people from majority Muslim nations—as evidence of bias on the special counsel team.
The president’s legal team has largely stayed quiet on the issue. But with Mr. Mueller’s investigation appearing to edge closer to Mr. Trump’s family and inner circle, the president is being urged to drop his team’s mostly cooperative approach to date.
“The president’s lawyers are sleepwalking their client into the abyss,” said Roger Stone, an adviser to Mr. Trump’s 2016 campaign whose dealings with WikiLeaks are under examination as part of the Russia investigation. “They are entirely unrealistic about the enmity toward the president from the political establishment, and the established order” Mr. Stone added.
Jay Sekulow, a member of the president’s personal legal team, said: “We’re pleased with the progress we’ve made. We remain confident with regard to the outcome.”
Defenders of Mr. Mueller, who is a Republican and a former longtime FBI director, say he is conducting an apolitical investigation into serious allegations of wrongdoing.
Mr. Mueller is investigating allegations of Russian interference in the 2016 presidential election and whether the Trump campaign colluded with Moscow. Mr. Trump has said his team did nothing wrong, and Russia has denied meddling in the election.
Federal law prohibits the Justice Department—which includes the special counsel’s office—from using political or ideological affiliations to assess applicants for career positions in the agency. Employees are also allowed to express opinions on political subjects privately and publicly, as long as they aren’t in concert with a political party or candidate for office.
Some of the president’s associates say they want the White House to set up a classic “war room” to respond to the probe, hire attorneys more inclined to challenge Mr. Mueller or to spotlight what they see as an anti-Trump animus on the part of the special counsel.
At a House Judiciary Committee hearing on Thursday, Republicans focused on Mr. Strzok and Mr. Weissmann, who sent an email to former acting Attorney General Sally Yates the night she was fired applauding her decision to instruct Justice Department lawyers not to defend Mr. Trump’s initial travel ban.
“I am so proud,” Mr. Weissmann wrote in the subject line of an email, which was released by the conservative group Judicial Watch. Mr. Weissmann also attended Hillary Clinton’s election-night party at the Jacob K. Javits Center in New York, according to people familiar with his attendance.
At the time, Mr. Weissmann was running the Justice Department’s fraud section, which is a senior career post within the agency.
In his current role, Mr. Weissmann has been leading the case against Paul Manafort , the former Trump campaign chairman, and Rick Gates, a campaign aide. Both men have been indicted on lobbying and financial crimes, charges they deny and which aren’t related to the Trump campaign.
Rep. Steve Chabot (R., Ohio), a Judiciary Committee member, called the “depths of this anti-Trump bias” on the team “absolutely shocking.”
A spokesman for the special counsel’s office declined to comment on Mr. Weissmann.
Democrats characterized the GOP bias allegations as an effort to discredit a legitimate investigation.
“I predict that these attacks on the FBI will grow louder and more brazen as the special counsel does his work, and the walls close in around the president, and evidence of his obstruction and other misdeeds becomes more apparent,” said Rep. Jerrold Nadler of New York, the House committee’s top Democrat.
Mr. Mueller appears to be mindful of potential conflicts or appearances of conflicts in his investigation. He removed Mr. Strzok “immediately upon learning of the allegations,” according to special counsel spokesman Peter Carr. Still, congressional Republicans said it was months after Mr. Strzok’s reassignment that federal officials disclosed the reasons why it happened. Mr. Strzok couldn’t be reached to comment.
The special counsel team also was interested in hiring another prosecutor from the fraud section, according to people familiar with the matter, but didn’t proceed because the prosecutor’s spouse works for Sen. Dianne Feinstein (D., Calif.), the ranking member on the Senate Judiciary Committee. That panel is conducting its own Russia investigation.
When then-President Bill Clinton faced off against an independent counsel, Kenneth Starr, in the 1990s, his allies worked to discredit Mr. Starr and paint him as a partisan—an approach that some of Mr. Trump’s confidants said they would like to emulate.
Steve Bannon, former White House chief strategist who continues to occasionally advise the president, has been critical of Mr. Trump’s legal team, and a person close to Mr. Bannon said he expects the former strategist to continue “pointing out the inadequacies” in the president’s legal strategy. Mr. Bannon wasn’t available for comment.
Suggestions that Mr. Trump shake up his legal team also follow what critics see as a series of missteps over recent months. A tweet sent from the president’s account, which lawyer John Dowd said he wrote, appeared to overstate what the president knew about his former national security adviser’s interactions with the FBI. That former aide, Michael Flynn, pleaded guilty this month to lying to federal agents. Two of his lawyers, Mr. Dowd and Ty Cobb, sat at a popular Washington steakhouse in September and talked openly about the case with a reporter in earshot.
Asked earlier this year whether the president was happy with his legal team amid criticism from outside advisers, White House press secretary Sarah Huckabee Sanders said, “I’m not sure how he couldn’t [be].”
While Trump lawyers say they have at times clashed among themselves, including over whether to assert executive privilege on certain documents, their general consensus has been that cooperation would help bring the investigation to a rapid close.
Mr. Cobb, who initially said the probe would wrap up by year’s end if not sooner, stands by his assessment that it’s moving at a reasonable clip. “I don’t see this dragging out,” he said in a recent interview. Mr. Mueller’s team is “committed to trying to help the country and get this done quickly,” Mr. Cobb said, adding, “I commend them for that. And we’re certainly determined to do it.”
—Rebecca Ballhaus contributed to this article.