The 568-page report by Justice Department Inspector General Michael Horowitz entitled “A Review of Various Actions by the Federal Bureau of Investigation and Department of Justice in Advance of the 2016 Election” is released. (Jim Bourg/Reuters)

Thursday’s report from the Justice Department’s inspector general gave new and potent ammunition to President Trump and his allies in their ongoing efforts to undermine special counsel Robert S. Mueller III’s investigation of Russian interference during the 2016 presidential campaign.

Even as Trump faces his own legal complications, Republicans quickly seized on the report as a meaningful development that they believe will further bruise Mueller’s credibility with the public and bolster the president, whose administration has long been gripped by the probe.

The clamor over the watchdog’s findings was the latest turn in the GOP’s increasingly hostile and preemptive offensive against Mueller’s expected report on the president’s conduct. And the furor is almost tailor-made for Trump, who throughout his career has clutched onto small details and controversy as weapons he uses to define his enemies and erode trust in institutions.

Particularly notable, from the perspective of Trump’s allies, was the searing criticism in the report reserved for the conduct of one of Trump’s most high-profile critics, former FBI director James B. Comey, as well as the revelation that lead FBI agent Peter Strzok had shown anti-Trump bias. “We’ll stop it,” Strzok wrote in a text message, referring to Trump’s presidential campaign.

White House press secretary Sarah Huckabee Sanders said the report “reaffirmed the president’s suspicions about Comey’s conduct and about the political bias of some members of the FBI.”

On Capitol Hill, there was an outcry. Sen. Lindsey O. Graham (R-S.C.), a Trump ally, said Thursday that he would support a new federal probe of Mueller’s special counsel investigation. “You’re going to need independent eyes,” he told reporters.

Democrats, as they have for months, sought to defend the sanctity of the special counsel’s inquiry. They said Mueller’s mission should not be attacked because FBI agents behaved inappropriately.

“None of this reflects on the special counsel’s work,” said Rep. Adam B. Schiff (Calif.), ranking Democrat on the House Intelligence Committee.

Republicans, however, sought to use the report to tarnish investigators.

Since the Strzok text message had not been previously disclosed to Congress, a number of Republicans immediately asked whether the Justice Department had purposefully hidden that missive from them.

Republican Reps. Andy Biggs (Ariz.), Matt Gaetz (Fla.) and Ron DeSantis (Fla.) — all Trump supporters — sent the Justice Department a letter Thursday demanding that the inspector general turn over all previous reports to see if “people may have changed the report in a way that obfuscates your findings.”

The coming political storm, spurred by the report, may only deepen the divide between those who see the Mueller investigation as a nonpartisan endeavor and those who argue it is the product of an anti-Trump “deep state,” a conspiratorial term the president and his Republican allies have used to describe some federal employees who they suspect could be working against Trump and his administration.

Trump-allied Republicans on Thursday put the inspector general report atop their pile of grievances, once again casting the Justice Department as biased and defending Trump’s decision to fire Comey — though the report criticized Comey for his handling of the Hillary Clinton email investigation.

In recent months, additional pressure on the Mueller probe has come from conservative lawmakers in the House Freedom Caucus as well as from Trump lawyer Rudolph W. Giuliani’s incendiary tour of cable TV.

“The FBI didn’t want Trump to be president,” Rep. Jim Jordan (R-Ohio), a leader of the Freedom Caucus, tweeted Thursday. “This is as wrong as it gets.”

But in a Washington defined by the dichotomy between warring political tribes, the reality of the Trump presidency and what each new investigative development means is now seemingly defined by the reality of whom you ask.

Polls show that Republicans see a despised “witch hunt” under siege. Many of them no longer trust officials at federal ­law-enforcement institutions. GOP lawmakers have cheered Trump’s return from a meeting with North Korean leader Kim Jong Un, and they credit Trump with what they see as a surging economy.

Democrats, meanwhile, see a beleaguered and defensive president, tweeting angrily as he awaits the upcoming trial of his former campaign chairman Paul Manafort and watches his longtime lawyer, Michael Cohen, face intensifying federal scrutiny. They anxiously await Trump’s possible sit-down interview this summer — or the subpoena battle that could follow, should he refuse to meet with investigators.

Eroding public support for Mueller is part of the GOP cause. A Quinnipiac University survey this month found 50 percent of registered voters saying Mueller was conducting a fair investigation, with 35 percent saying he was not.

Although the poll showed a positive rating for Mueller, it marked the lowest percentage saying his investigation was fair since Quinnipiac began asking in November, when 60 percent of voters said the investigation was fair. And it showed where the attacks by Trump and his allies have been effective — with just one-quarter of Republicans saying the inquiry is fair.

Mueller, who remained characteristically silent Thursday, is trying to secure an interview with Trump in the coming weeks so he can finish his report on possible obstruction of justice. He has told Trump’s lawyers that he would like to complete that report within 90 days of interviewing Trump and well before this year’s midterm elections — a timeline that could be upended if the president and Giuliani continue to resist giving him a final answer.

As Mueller waits, the inspector general report will be the latest cudgel in the Republican arsenal. The White House’s perspective was echoed throughout the conservative press and on social media, where a blizzard of tweets and posts called the report a sudden breakthrough moment for Trump.

The inspector general’s conclusions were viewed through a political lens and seen by most Republicans as somewhat helpful in uncovering evidence, but little more than that.

“I understand that it’s very difficult for the IG to draw conclusions absent . . . admissions, confessions,” said Senate Homeland Security and Government Affairs Committee Chairman Ron Johnson (R-Wis.). “I drew my own conclusions quite some time ago that this was not an investigation designed to uncover the truth.”

What makes this GOP effort different and potentially so challenging for Mueller is how it emanates from the center of Republican power rather than from the fringes. It is the president and GOP members of Congress who are happily taking up the rhetorical ax each day, swinging away at the investigation being led by a former FBI director who they praised just a year ago.

Giuliani and Trump — two bellicose New Yorkers and generational peers — are driving the tone and scope of the barrage, deliberately breaking from the more cooperative approach that Trump’s former lawyers John Dowd and Ty Cobb once advised until they resigned.

“Defense to offense,” Giuliani recently told The Washington Post when asked about the strategy. “All offense.”

Scott Clement and Karoun Demirjian contributed to this report.