North Charleston, South Carolina (CNN) An ebullient Lindsey Graham hopped off the stump here after revving up a room full of conservative voters, reliving his furious defense of now-Supreme Court Justice Brett Kavanaugh at his confirmation hearings and making clear he was on President Donald Trump's side.

After streams of voters lined up to take selfies with Graham last week, the detractor-turned-Trump-defender was asked: Is there any room for a Trump critic in today's Republican Party?

"I don't think there's any room in the party for wanting him to fail," Graham, a South Carolina Republican and now a chief Trump ally, recently told CNN. "If they see your criticism is designed to want him to fail or not support him, then you're in trouble."

Graham quickly added: "Most people in that room want me to stay close to the President."

Heading into his first midterm election as President, Trump has effectively silenced once-vocal GOP critics inside the Republican Party -- including Graham from just months ago -- a sign of the rapid makeover of the party underway since Trump took office in 2017. He commands near loyalty from his base -- with a whopping 9-out-of-10 GOP voters approving of his performance in office, according to a recent Wall Street Journal-NBC News poll.

GOP voters have little patience for sharp critics like Arizona Republican Sen. Jeff Flake, whom just 22% of national Republican voters view favorably in a recent CNN poll and admittedly had to quit for fear of losing a primary in Arizona. Republicans in swing states such as Sen. Dean Heller in Nevada -- where the anti-Trump sentiment is rabid among Democrats and Hispanic voters -- have calculated it makes far more sense to tie themselves closely to Trump, rather than risk the ire of his supporters by running away from the President.

All of that has made Trump an unusually powerful figure in his party despite historically low approval ratings among the broader electorate and standing as the most polarizing figure in American politics. The dynamic puts Republicans in an ongoing dilemma in dealing with a President who shatters all norms, speaks falsehoods regularly and dabbles daily in new controversies: They can speak up against Trump and win over their critics but risk the wrath of Trump -- and his supporters -- in the process.

"The bottom line is the people who want me to criticize the President want him to lose," Graham said in an interview. "I want him to win. I want him to be successful. He beat me. The election is over. I intend to work with him where I can. Did it with Obama. Did it with Bush. Nothing new about that."

And Graham, who admits "President Trump can be a handful," makes the case clearly: Staying on Trump's good side gives him constant access to the President -- and the ability to shape the views of a man known for acting impulsively. He said he's talked to the President "more than all other presidents combined," saying Trump now has two of his phone numbers after then-candidate Trump famously announced Graham's telephone number in 2015 at a GOP rally to mock the South Carolina senator.

His advice now for Trump: "Mr. President, if you get mad at me, call me."

Courting conservative skeptics

For Graham, 63, the embrace of Trump marks an evolution from the days he was a leading Trump critic and was a man with a reputation for bipartisan deal-cutting that irked the conservative base. Yet his latest positioning has bolstered his own standing back home and around the country, winning positive marks from 59% of GOP voters nationally, according to a CNN poll from earlier this month.

Graham faced seven conservative primary opponents in 2014, but with staunch Trump backing, he's now on solid footing with the conservative base ahead of a run for a fourth Senate term in 2020, according to Republican operatives here in the state.

The South Carolina Republican was once reviled by the Republican base for supporting comprehensive immigration legislation, backing then-President Barack Obama's Supreme Court nominees, and allying himself closely with the late Sen. John McCain, who long had a rocky relationship with the conservative movement.

But conservative voters who have been skeptical about Graham in the past say they're on the team now.

Asked if he supported Graham in his last run, Stephen Wright, a GOP voter in South Carolina who backed Ted Cruz for president in 2016, said: "Absolutely not."

Now, things are different. "Right now, barring he doesn't make a major mistake or doesn't continue his conservative track record that he started this year, I think I could" support his re-election, Wright said.

Some Republicans believe businessman John Warren, a self-funder who lost a GOP primary in the governor's race here this year, may ultimately mount a challenge to Graham in his Senate race.

In an email, Warren was coy when asked if he would consider running against Graham.

"I applaud Sen. Graham in his recent support of conservative values," Warren said, adding that it's "vitally important" conservative judges like Kavanaugh. "I can only hope that he will continue in his newfound conservatism and tackle issues such as border security and limiting the size of the federal government."

Yet Graham — who says, "I've come to like the President" and supports much of his agenda -- denied his positioning had anything to do with his 2020 reelection ambitions.

"I want to show the people of South Carolina who elected me that I'm mature -- that I will accept defeat because I ran against him," Graham said when asked about the 2020 speculation.

Kavanaugh hearing spotlight

Graham's efforts to shore up the conservative base were rapidly bolstered when he furiously defended Kavanaugh from sexual misconduct allegations that were imperiling his nomination to the Supreme Court.

At last month's high-stakes hearing on the matter, Graham was sitting back and listening to Democratic Sen. Dick Durbin raise the specter of a broader investigation into Kavanaugh's past. The Republican senator immediately decided to intervene, yanking the question time away from the outside prosecutor the GOP hired to question the witnesses.

"This is the most unethical sham since I've been in politics," Graham said, shouting at his Democratic colleagues, rallying GOP senators to Kavanaugh's defense.

As Graham now recounts the episode across the country in key midterm battlegrounds, raucous GOP voters roar in appreciation.

"I was really pissed," Graham said last week to the North Charleston crowd, which erupted into applause. "They believe it is a noble cause to destroy a conservative. I don't believe that. I do not believe that. I don't want power that badly. If you want it that bad you're not worth a damn to anybody."

Graham, his voice rising, told the crowd: "This is not the Soviet Union. This is the United States. I wanted to let them know not how I felt but how you felt."

The newly found celebrity status has sent Graham to 12 states with key House and Senate races in the final two weeks leading up to the midterms, making him one of the GOP top surrogates on the campaign trail -- a highly unusual position within the party during his more than two decades on Capitol Hill.

Now, Graham is getting a reception like one he has seldom heard before in his career -- greeted like a rock star at Republican events.

"The reception out there today was about Kavanaugh," Graham told CNN last week after firing up a room of roughly 100 GOP voters while stumping for House candidate, Katie Arrington, who is facing a challenge from Democrat, Joe Cunningham, in November.

A reliable GOP seat now at risk of flipping

In this district, Republican officials are now quick to embrace Trump, who defeated Hillary Clinton by 13 points here in 2016. Arrington won her primary this summer against Republican Rep. Mark Sanford, who lost in large part because of his regular criticism of the President. But suddenly, Republicans are getting nervous about the seat flipping, with national Republicans pouring in late money to try to fortify her position.

To try to fire up her base, Arrington delivers her stump speech in a Trumpian tone, railing on the news media, demanding that the border wall be built and even suggesting her opponents are "evil."

"I got criticized for saying this a war between good and evil but by God when you're willing to put people down, spread vicious lies and talk about our veterans in such a manner, it is good and evil," Arrington said. "And I'm alright with that."

As she walked off stage and worked the room, Arrington dodged reporters, escaping through a kitchen when asked by CNN if she believed there was any room for Trump critics in the Republican Party.

Graham, himself, says there will be issues with which he disagrees with the President -- immigration being one, where he says he still backs a pathway to citizenship for people here illegally and shies away from the dark rhetoric the President uses to castigate undocumented immigrants. But on Tuesday, Graham backed up Trump's call to end birthright citizenship, calling it an "absurd policy" he's long opposed. The right to citizenship for anyone born in the United States is guaranteed in the 14th Amendment to the Constitution.

"Most illegal immigrants are not drug dealers or rapists," Graham told CNN. "They're hard working people who come from very corrupt places where it's unsafe. But we've got to have order out of chaos."

Yet, many Graham critics want him to do more -- and speak up more forcefully against Trump, as his close friend McCain did in the final months of his life.

"John was tough, but he was forgiving," Graham said. "I'm not going to worry about John McCain in what I would do because I loved the man."

Graham added: "He would work with the President where he could and he would still be John McCain."