Washington (CNN) President Donald Trump expressed guarded optimism on Tuesday his Supreme Court nominee Brett Kavanaugh will soon be confirmed, even as he grows more frustrated by the delays and scandal plaguing a confirmation process he once believed bulletproof .

It was the second day in a row Trump has flashed with discontent at the nomination process, which he once believed -- based on predictions from aides -- would be complete by the start of the Supreme Court's term this week. Watching Kavanaugh mired in allegations of decades-old drunkenness , Trump has become exasperated the "central casting" nominee he selected is now viewed differently by much of the country.

"I think that Judge Kavanaugh's doing pretty well, it seems to me, over the last 24 hours," Trump told reporters before departing for Philadelphia, where he was speaking to a group of electricians. Citing Senate Majority Leader Mitch McConnell, with whom he's grown annoyed over his handling of the Kavanaugh matter, Trump expressed his wish for a Friday vote.

"Hopefully, as Mitch said, they'll have a vote by the end of the week and it will be a positive vote," he said.

Still, Trump warned that lying to Congress -- which Kavanaugh has been accused of by a Yale classmate and Democratic senators -- would cross a line: "For me, that would not be acceptable."

And he again held out the prospect that an ongoing FBI investigation into the sexual assault claims levied against Kavanaugh could amount to a deal-breaker. White House counsel Don McGahn, a close friend of Kavanaugh's who led his nomination process, has been kept abreast of developments in the FBI's investigation since the White House officially called for it last Friday, people familiar with the matter said.

Multiple witnesses, including Kavanaugh's high school friend Mark Judge, have been interviewed.

"A lot is going to depend on what comes back from the FBI," Trump said. "The FBI is working. They're working very hard. And let's see what happens."

It was another shot of cautious optimism in a process that has stretched well beyond the President's expectation when he first selected Kavanaugh to fill a vacant Supreme Court seat in July. Back then, Trump thought he'd found his judicial ideal: a Yale-educated family man with a thick head of hair and the strong backing of conservatives.

"Is this central casting? This is what we want," he told a Charleston, West Virginia, crowd in August. "He's central casting," he repeated in September, speaking to an audience in Fargo, North Dakota. "The intellect is extraordinary, and the man is extraordinary."

Now, that vision of a justice plucked straight from a casting director's binder is complicated by decades-old allegations of debauched beach weeks and drunken bar fights. For Trump, the changing portrait has become another letdown in a nomination process gone awry, even as he staunchly defends his nominee and presses Congress to confirm him.

"When he was chosen, everybody said, 'Oh, this is going to go so quickly,' " Trump said on Monday, blasting Democrats for not raising allegations of sexual assault earlier in the process.

Lashing out

Privately, however, Trump hasn't focused his ire solely on Senate Democrats. While publicly holding his tongue, Trump has privately lashed out at McConnell for allowing Kavanaugh's confirmation process to devolve into chaos.

Last week, the President told confidants he planned to discard McConnell's advice on how to respond to the allegations against Kavanaugh from Christine Blasey Ford, the California professor who accuses Kavanaugh of sexually assaulting her in high school. Kavanaugh has denied the allegation. After the President publicly cast doubts on Ford's credibility in a tweet, McConnell advised him over the phone to desist.

In recent days, Trump has complained the Kentucky senator let the drama surrounding the Supreme Court nominee get out of hand. McConnell has responded to that criticism by appearing on the Senate floor every day for the last week -- with the exception of Thursday, when Kavanaugh testified in front of the Senate Judiciary Committee -- to vehemently defend Kavanaugh while placing the blame squarely on the Democrats.

McConnell repeated Tuesday his promise to hold the Kavanaugh vote this week, even as an FBI investigation into the multiple allegations is still underway.

"One thing we know for sure -- the Senate will vote on Judge Kavanaugh here on this floor this week," McConnell said, adding that Democrats "will not be satisfied unless they have brought down Judge Kavanaugh's nomination."

Bringing Kavanaugh's nomination to a vote this week will require the conclusion of the FBI investigation that some senators requested last Friday. Whether the results of that probe are made public remains to be seen. Trump did not answer a question Monday about whether the White House will release the FBI's findings once the additional inquiry into Kavanaugh's background is completed.

Even as the investigation into allegations of sexual assault proceeds, senators are weighing other questions raised by Kavanaugh's fiery and angry testimony last week. His overtly political opening statement -- blasting the accusations against him as an attempt to exact "revenge on behalf of the Clintons" -- has drawn criticism from Democrats. And his angry demeanor, which included interrupting senators, has sat poorly with some lawmakers.

"The interaction with the members was sharp and partisan, and that concerns me," Sen. Jeff Flake, a key Republican fence-sitter, said on Tuesday in an appearance at The Atlantic Festival in Washington. "I tell myself, you give yourself a little leeway because of what he's been through, but on the other hand, we can't have this on the court."

A tale of two Kavanaughs

Meanwhile, Kavanaugh's description of his teenage drinking and love for beer has drawn eye-rolls and mockery, including in an exaggerated impression by Matt Damon on NBC's "Saturday Night Live."

On Monday, instead of touting the "central casting" character he hopes will eventually be confirmed, Trump implied Kavanaugh once had a drinking problem.

"I was surprised at how vocal he was about the fact that he likes beer," Trump said in the Rose Garden. "And he's had a little bit of difficulty. I mean, he talked about things that happened when he drank."

Kavanaugh admitted in congressional testimony that in high school and college, "sometimes I had too many beers." But he stopped short of acknowledging a drinking problem. And he blamed apparent references to vomiting in his high school yearbook to a weak stomach.

On Tuesday, Trump -- who once wrote in a book that "drinking too much or behaving inappropriately is a one-way ticket to the Z-list" -- shrugged off the accounts of excessive drinking.

But he again raised his own aversion to alcohol, a substance he's avoided after his older brother Fred died from alcoholism in the 1980s. And he made clear that he did not share his nominee's professed affinity for beer.

"I don't drink beer. I've never had a beer," he said. "And I'm not saying good or bad. Some people like it. I just chose to do that for a lot of reasons."

"I remember my college days, everybody was drinking," he went on. "It was like normal. I was abnormal. It was totally normal everybody was drinking. And they used to drink a lot of beer and there was nothing wrong. I just didn't choose to do that. But almost everybody else did. So I don't see anything wrong."