Kavanaugh's seemingly obstacle-free path to a seat on the high court suffered a major setback in mid-September, when California psychology professor Christine Blasey Ford went public with her allegation that an intoxicated Kavanaugh tried to rape her in the early 1980s when they both were teenagers.
Shortly after, The New Yorker published an allegation from Kavanaugh's former Yale University classmate Deborah Ramirez, who said he had exposed himself to her while drunk at a college party in the '80s.
Kavanaugh categorically denied both allegations, and agreed to testify along with Ford in a Senate Judiciary Committee hearing on Sept. 25. He angrily defended himself, telling the committee, "I've never sexually assaulted anyone."
Just a day before the hearing, however, Avenatti dropped a bombshell in the form of a sworn declaration from Swetnick, who made jaw-dropping claims against Kavanaugh and others in his group of friends from the early 1980s.
Swetnick said she "became aware of efforts" by Kavanaugh and other boys to "'spike' the 'punch' at house parties" to get girls to "lose their inhibitions and their ability to say 'no.'" Swetnick's statement also claimed she had been "the victim of one of these 'gang' or 'train' rapes."
Republicans immediately pounced on her allegations. Sen. Lindsey Graham, R-S.C., Kavanaugh's most passionate defender throughout the confirmation process, slammed Avenatti in a statement while expressing extreme skepticism toward Swetnick.
"The lawyer to porn stars has just taken this debacle to an even lower level," Graham said in the statement, which used Avenatti's name six times.
"I'm not going to have my intelligence insulted by the Michael Avenattis of the world. I will not be a participant in wholesale character assassination that defies credibility," Graham said.
Senate Judiciary Committee Chairman Chuck Grassley, R-Iowa, also questioned Avenatti's motives and his past. "It seems to me he wants to protect people that are involved in pornography and that he's running for president," Grassley said.
Grassley and Graham had both signaled support for Kavanaugh early in the process. But Avenatti was also rebuked by Sen. Susan Collins of Maine, a moderate Republican and crucial swing vote, in her lengthy speech Friday announcing that she would vote to confirm the embattled judge:
"Some of the allegations levied against Judge Kavanaugh illustrate why the presumption of innocence is so important. I am thinking in particular not of the allegations raised by Professor Ford, but of the allegation that, when he was a teenager, Judge Kavanaugh drugged multiple girls and used their weakened state to facilitate gang rape.
"This outlandish allegation was put forth without any credible supporting evidence and simply parroted public statements of others. That such an allegation can find its way into the Supreme Court confirmation process is a stark reminder about why the presumption of innocence is so ingrained in our American consciousness."
A few days earlier, Collins, in a statement to the Portland Press-Herald, called for the FBI to look into the claims brought against Kavanaugh, including "the allegations that were brought by Julie Swetnick." But Trump's "limited in scope" order did not permit the FBI to interview Swetnick or a number of other witnesses.
Collins' office did not immediately respond to CNBC's inquiries.
Collins' announcement was followed minutes later by Democratic Sen. Joe Manchin of deep-red West Virginia who said he, too, would vote to confirm Kavanaugh. The late-breaking tallies in the "yes" column effectively ensured that Kavanaugh had clinched the seat.
Avenatti slammed Collins in a statement to CNBC at the time. "I have no idea what she is talking about and evidently neither does she," he said. "How the hell did Susan Collins make a credibility determination related to my client's allegations when she never did any investigation whatsoever?"
A slew of Democratic senators and aides told CNN's Manu Raju that Swetnick's allegations provided cover for them to vote for Kavanaugh without having to specifically question Blasey Ford, who was widely viewed as being a credible figure.
"Not helpful at all," one Democratic senator who requested anonymity told CNN. "I think Susan was always yes, but Avenatti was a useful foil."
Some media figures also pointed to Avenatti as a liability in the confirmation battle.
Avenatti's use of social media and his willingness to call out his political enemies has drawn parallels to Trump, who is praised on the right and damned on the left for always "fighting back" against his critics.
Like Trump, Avenatti "is quite good at securing coverage and leveraging the media for coverage and it shows in both social virality and news stories/interviews," said Barbara Kittridge, founder of progressive strategy group Motive.
Kittridge told CNBC in an email that Avenatti did shift the conversation, thought it was unclear if he affected the outcome.
"In the sense that Avenatti has the ability to take a great deal of the oxygen out of a room, yes we saw a quick and marked shift of the spotlight," Kittridge said, "from the credible testimony of Dr. Blasey Ford, to Avenatti and his client's claims against Kavanaugh."