WASHINGTON – A day after Attorney General William Barr cleared President Donald Trump of conspiring with Russians to win the 2016 election, Republicans in Congress said they would open a new probe into the investigation Trump derided as an "illegal takedown that failed."

Senate Judiciary Chairman Lindsey Graham, R-S.C., told reporters Monday he has urged since late 2017 a review of the justification for surveillance warrants against Carter Page, a foreign-policy adviser to the Trump campaign that were based in part on a "dossier" of salacious material collected by former British intelligence worker Christopher Steele, who was hired by Democrats to investigate Trump.

“Whether or not it’s illegal, I don’t yet know,” Graham said. “What makes no sense to me is that all of the abuse by the Department of Justice and the FBI – the unprofessional conduct, the shady behavior – nobody seems to think that’s much important. Well that’s going to change, I hope.”

Graham, a former military lawyer himself, also questioned why the FBI did not warn the Trump campaign about repeated Russian efforts to influence him, as documented by special counsel Robert Mueller. Graham said his question is whether the counterintelligence investigation was opened “as a back-door to spy on the campaign.”

Republicans in the House of Representatives spent months investigating similar questions when they controlled the chamber last year, producing incendiary messages in which FBI agents professed their disdain for Trump, but no direct evidence that the Justice Department's conduct was motivated by political considerations. The department's Inspector General also is conducting a review of the Russia investigation.

“I still to this day am at a loss to explain why nobody went to President Trump to tell him that there may be some people in your orbit that are connected to the Russians and working with the Russians,” Graham said. “How did it fail and break down here? What it a ruse to get into the Trump campaign? I don’t know, but I’m going to try and find out.”

Graham outlined his priorities after Barr summarized the conclusions of Mueller's 22-month investigation of Russian interference in the 2016 election. Barr said Mueller found no Trump campaign conspiracy with Russia. Mueller made no decision on whether Trump obstructed justice, but Barr and Deputy Attorney General Rod Rosenstein found insufficient evidence to pursue an obstruction charge.

Trump himself claimed vindication from Barr’s summary.

But House Judiciary Chairman Jerrold Nadler, D-N.Y., said Barr's conclusions merely handed the job of investigating Trump to Congress, whose judgments aren't strictly constrained to whether someone committed a crime.

“It is unconscionable that President Trump would try to spin the special counsel’s findings as if his conduct was remotely acceptable,” Nadler told reporters Sunday. “Special counsel Mueller was clear that his report ‘does not exonerate’ the president.”

Both Graham and Nadler each said they will call Barr to testify about his decisions.

Even before Mueller submitted his confidential report to Barr on Friday, a poll in mid-March found the country divided about whether Democrats were "going too far" in their investigations.

The USA TODAY/Suffolk University Poll of 1,000 registered voters found nearly 49 percent said "Democrats are doing the right thing in these investigations," while 46 percent said "Democrats are going too far with all the investigations." The poll was taken by landline and cellphone March 13 through 17, and had a margin of error of plus or minus 3 percentage points.

Congressional Republicans have long argued that the FBI began investigating Trump during the campaign because of political corruption aimed at defeating him. The FBI fired former agent Peter Strzok, who exchanged anti-Trump messages with FBI lawyer Lisa Page.

Trump later fired former FBI Director James Comey. Republicans considered the dismissal of the political appointee justified, but Democrats and some legal experts have argued is a possible justification for an obstruction charge.

Graham’s priorities listed have concerned House Republicans for years, as he noted.

“Those days are over,” Graham said. “Going forward, hopefully in a bipartisan fashion, we will begin to unpack the other side of the story.”

More on the political landscape after special counsel Robert Mueller's inquiry:

Analysis: With Mueller report in, nothing's over. But for Trump, everything has changed

Poll: Half of Americans say Trump is victim of a 'witch hunt' as trust in Mueller erodes

Congressional Democrats question AG William Barr's decision that Trump didn't obstruct justice

Mueller’s report found no Russia collusion, but vindication remains elusive for Trump