"Senate Republicans are taking steps to issue new subpoenas to a wide variety of Obama administration officials with some relationship to the abuses," McConnell said in a floor speech Tuesday, referencing errors made with the surveillance of a former Trump campaign official and the prosecution of former Trump national security adviser Michael Flynn, which the Department of Justice has moved to dismiss. "The American people deserve answers about how such abuses could happen, and we intend to get those answers."
The notable move by the Republican leader, who once supported the Mueller probe and is a strong supporter of the foreign surveillance laws, came after the president tweeted over the weekend, "Mitch, I love you, but this is 100% true. Time is running out. Get tough and move quickly, or it will be too late. The Dems are vicious, but got caught. They MUST pay a big price for what they have done to our Country. Don't let them get away with this!"
The president traveled to Capitol Hill Tuesday, in part, to hammer home that very message in a closed-door lunch with Senate Republicans, according to four GOP senators.
Attendees said afterward that Trump encouraged the group to "get tough" on the federal investigators he has long decried as "corrupt," those who led the probe known as "Crossfire Hurricane." He also encouraged them to unify and fight back because -- he said -- Democrats will continue to stick together to attack him.
After the lunch, the president brought the subject up on his own with reporters, echoing an oft-repeated rallying cry on the campaign trail, saying, "The top of the FBI, they were dirty cops. They were crooked. Bad people, and nobody has been abused more than Trump."
Special counsel Robert Mueller's nearly two-year investigation found no conspiracy between the Trump campaign and the Russians, but it stopped short of exonerating the president on obstruction of justice.
"If we had confidence after a thorough investigation of the facts that the President clearly did not commit obstruction of justice, we would so state. Based on the facts and the applicable legal standards, however, we are unable to reach that judgment," the report read.
Still, Republicans are intent on plowing back through the probe.
"The government's case against (Trump) was unfair and distorted as well. Wild theories of Russian collusion, but upon investigation -- the Mueller investigation, remember that one? It was those wild allegations that collapsed," McConnell said. "No matter what Washington Democrats try to claim, you're not crazy or a conspiracy theorist if you see a pattern of inconsistency toward this president. You'd have to be blind not to see one."
The Senate Judiciary Committee, led by top Trump ally Chairman Lindsey Graham, announced Monday that it will seek authorization to issue subpoenas for Obama-era intelligence and law enforcement officials like former FBI Director James Comey, former Director of National Intelligence James Clapper and former CIA Director John Brennan.
Graham, R-S.C., is honchoing the sweeping probe of the investigation by Mueller -- whom the chairman has praised in the past -- and a deep dive into the significant problems inside the FBI regarding how it went about obtaining permission from a secret court under the Foreign Intelligence Surveillance Act to surveil then-Trump campaign senior adviser Carter Page.
The chairman said he hopes to have a preliminary report ready in October, which would place it squarely in the middle of the presidential campaign.
And Graham is not alone in his efforts that could have major political consequences in the fall.
Senate Homeland Security Committee Chairman Ron Johnson, R-Wis., is hoping to gain the support of a majority on his panel Wednesday in order to issue a subpoena for documents from Blue Star Strategies, a Democratic firm that sought influence in the Obama administration on behalf of Ukraine energy giant Burisma. The investigation is intended, the chairman said, to seek out any improper actions by former Vice President Joe Biden's son, Hunter, who has maintained his innocence.
Johnson has partnered with Sen. Chuck Grassley, R-Iowa, who will take the gavel back at the Judiciary Committee if Republicans hold onto their majority in this year's elections.
Sen. Minority Leader Chuck Schumer called these investigations part of an "insane conspiracy theory" and part of an effort to "rewrite the history of Russian interference in the 2016 election to match the fantasy in the president's head."
"We're talking about some wild theory, because President Trump two days ago demanded it when everyone knows the president's penchant for truth is at a bare minimum, as exemplified by his hydroxychloroquine comments last night," Schumer said, referencing the president's announcement that he was taking an anti-malarial drug as a prophylactic against COVID-19, an unproven treatment regimen.
The vociferous, public support by McConnell was a remarkable moment for the majority leader, who has generally remained at arm's length when the president has lashed out at law enforcement and the Intelligence community in the past.
McConnell did not back Trump's candidacy in 2016 until later in the race, supporting former Florida Gov. Jeb Bush instead, so his Tuesday speech marked something of an evolution, one that perhaps represented a recognition that the political fate of the two men is now inextricably linked.
"I just think that everybody realizes that our fortunes sort of rise and fall together," said McConnell's chief deputy, Sen. John Thune of South Dakota. "One thing that we have to make sure that we are is united on our agenda and making sure that there's not separation between the White House and Republicans in Congress."
And with a grin that appeared to acknowledge the unique experience many senators have gone through in learning to deal with a mercurial president, Thune continued, "It's probably an evolution over time, to some degree, and part of it, too, is getting accustomed to each other's styles, differences in the way we do things. But you know, in the end, it's all about getting results, and I think that we're going to be judged by our accomplishments and our results."
But Schumer slammed Republicans for focusing on investigations rather than the coronavirus pandemic.
"The president is tweeting insane conspiracy theories, demanding that his water carriers of Capitol Hill make them look legitimate instead of focusing on testing capacity and policies to safely reopen our country."
ABC News' Allison Pecorin contributed to this report.