Sen. JD Vance knows he has had a rocky rollout as Donald Trump's running mate, but the Ohio Republican doesn't believe he has disappointed the former president.

"No," Vance told NBC News in an interview aboard his campaign plane en route to a rally here Tuesday. "I mean, I knew that when I came out of the gate there was going to be a couple of days of positive media coverage and then immediately they would go and attack me over everything that I had ever said in my life."

Vance has faced relentless criticism from allies of Vice President Kamala Harris, the de-facto Democratic presidential nominee, for his 2021 comments questioning the societal value of women who don't have children and referring to them as "childless cat ladies." Harris' campaign over the last week has attempted to brand Vance and his political point of view as "weird." Trump has stood by Vance.

"The price of entry of being on the national ticket and giving me an opportunity to govern is you have to ... take the shots, and so I sort of expected it," Vance said. "I think that, frankly, the people who've made a lot of money and acquired a lot of power screwing the country up are not going to go easily."

Vance is in the midst of a big Western swing that includes California fundraisers, traditional campaign rallies and a Thursday morning visit to the U.S.-Mexico border in Arizona. With his wife, Usha, seated next to him at the front of their chartered 737, Trump Force Two, Vance discussed the early days of his vice presidential campaign, as well as what he hopes to accomplish if the GOP ticket wins this fall.

"My attitude is, I want to be a good public servant," Vance said when asked what particular policy areas he would carve out for himself. "I'll help out wherever I'm asked to help out. Certainly I'd love to be given some influence over our border policy, and I'd basically do the exact opposite of what Kamala Harris did." 

This week's trip is a bit of a reboot meant to sharpen Vance's role as an attack dog against Harris, whom President Joe Biden endorsed as his successor when he ended his re-election bid days after Vance accepted the Republican nomination for vice president. While Harris backers have tried to define Vance as weird, Vance tried Tuesday to define Harris as weak — particularly on immigration and border security.

"It all starts with strength — strong borders, strong families, a strong economy and a strong president," Vance said in an afternoon speech at a high school in Henderson, Nevada, near Las Vegas. "Of all of Kamala Harris's faults, the worst of all is that she left America weak and vulnerable. The entire world now knows that she helped cover up Joe Biden's declining mental capacity for years."

"Our adversaries," Vance added, "are licking their chops and the world is in disarray because of weak American leadership."

Asked aboard his plane if the weird vs. weak contrast was intentional, Vance described it as more of a coincidence.

"I wouldn't say there's some particular effort to tag her as weak," he said. "If there's a particular label we want the American people to be aware of, it's that she's an ultra-liberal."

Aside from border issues, Vance said he could see himself in the Trump administration as a spokesperson on combating drug abuse. His mother, Beverly Aikins, is nearly 10 years sober after battling addiction — a struggle he wrote about in his best-selling 2016 memoir "Hillbilly Elegy" and talked about in his speech at this month's Republican National Convention. On the plane, Vance mentioned that he attends Narcotics Anonymous meetings "fairly frequently" with his mother to support her.

"One of the largest providers of medical care for people who have substance abuse disorder is Medicare," Vance said. "And another big one is Medicaid, right? So the federal government has a huge role to play, I think, in solving or at least addressing the substance abuse problem. I think one of the roles that I can play is just a basic leadership role, and remind people that there is hope on the other side of addiction — there is recovery."

Vance then connected the issue back to a central issue in his recent speeches: the border.

"For people to get second chances, they have to not die when they're at the bottom of the addiction crisis, and the best way to solve that problem is to prevent the worst poison from coming into our streets in the first place," he said, blaming Mexican drug cartels. "And if there's an attitude shift that I've seen over the last five years, the last three years, it's that there's so much fentanyl out there, and everything is laced with fentanyl, that the consequence of falling off the wagon could very well be death, right? There's a sense of fear in the addiction recovery space that I didn't notice five years ago." 

Vance got enthusiastic receptions in Henderson and Reno. At the first stop, after he noted that he will turn 40 on Friday, the crowd broke into a rendition of "Happy Birthday." He also has reinforcements on this trip. Jason Miller, a senior adviser on the Trump campaign, and Rep. Anna Paulina Luna, R-Fla., were among those traveling with him Tuesday.

"I'm here today because of the nasty attacks on JD Vance claiming that he's anti-woman," Luna said from the stage in Henderson. "Can you believe that? This is, mind you, by the same party that can't define what a woman is."

Speaking with reporters afterward, Luna, who traveled on Vance's plane, said no one asked her to make the trip. 

"It was actually me," she said. "I was like, you know, I have some things to say. So I kind of invited myself. But they're happy to have me."

On the plane, Vance stood by his old comments about childless women, which at the time he applied specifically to Harris, a stepmother of two, and other Democrats. Vance also said at the time that the criticism didn't extend to women who have trouble conceiving. 

"What I was criticizing and continue to criticize is a particular neurosis in American leadership that I think leads people to say crazy things, like you shouldn't have children because climate change is a threat to the future," Vance said Tuesday. "Climate change may very well be a problem, but it is not a problem that should motivate people to not have families. And I think that attitude is quite damaging. It's quite destructive.

"I'll keep on calling it out, even though I'm sure that Democrats will misrepresent what I say," he added. "I just think that the substance of what I said is actually quite defensible." 

Vance, who remarked last week that he was "pissed off" that he would no longer face Harris in a vice presidential debate, said he had no particular preference for a new opponent.

"I don't really care," Vance said. "I think that obviously different guys — and they're all guys, I guess, except for [Michigan Gov.] Gretchen Whitmer, but I don't feel like she has a good chance — they all present different strengths and different weaknesses. My attitude is I have a job, but it's to persuade as many people to vote for us as possible. And I'm going to have that same job whoever the Democrats nominate."