EDITOR'S NOTE: This story was originally published on December 28, 2017. Last week, Democrats announced that Rep. Joe Kennedy of Massachusetts will give the party's response to President Donald Trump's State of the Union address on Tuesday. Kennedy is also planning to bring US Army Staff Sgt. Patricia King , a transgender soldier, as his guest.

Washington (CNN) One congressman is a low-key member of a political dynasty who is strategically inserting himself into policy debates and laying out what he thinks Democrats still need to learn. The other is a retired Marine and combat veteran who has tangled with House Minority Leader Nancy Pelosi and has already logged a high-profile trip to Iowa more than three years ahead of the next presidential caucus.

Massachusetts Reps. Joe Kennedy III and Seth Moulton take different approaches to their work in Washington. But as Democrats focus on retaking the House next year, these lawmakers in their late 30s are getting a fresh look as potential future leaders in a party where many in the senior ranks are well into their 70s.

"Both are certainly talented enough to certainly be included in higher office and in greater roles and contributions in the country," said Rep. Steny Hoyer, the No. 2 Democrat in the House.

In interviews with dozens of House Democrats over the past several months, Kennedy and Moulton are both viewed as necessary new voices at a time when the caucus is growing restless. Publicly, their colleagues point to the Massachusetts lawmakers' contributions on national security and health care and say they can connect better with young constituencies.

But privately, some House Democrats say Kennedy is going about his next steps in a more methodical and collegial way, traveling to districts to help raise money and awareness on issues. Moulton is viewed by some as more eager to elevate his own profile, appearing regularly on cable outlets and repeatedly criticizing his own leadership.

For now, Kennedy and Moulton are thinking a lot about 2018, a year that is starting to show signs of being a potential wave election favoring Democrats. In this time of anti-Trump fervor, they're confident in the prospects of Democrats taking the 24 seats needed to reclaim the House majority for the first time in eight years. But first, they're urging their colleagues to internalize lessons from 2016.

In a recent interview after his fall trip to Iowa, Moulton says the message he delivers across the country is simple: Democrats need to turn to a new crop of leaders.

It's unequivocal, everyplace I go, the one line I can use in a speech that I know will get applause is when I say it's time for a new generation of leadership in our party

"It's unequivocal, everyplace I go, the one line I can use in a speech that I know will get applause is when I say it's time for a new generation of leadership in our party," Moulton said.

Kennedy, the great nephew of former President John F. Kennedy, headlined a recent Texas Democratic party dinner heavy on criticism of President Donald Trump, who he said launched an "all-out assault on America's character." But he also used the occasion to level some direct criticism at Democrats who spent time hand wringing after Trump's victory without relearning what he described as a basic lesson about politics.

"Do not underestimate what it means to be able to provide for your family and how deeply it destroys you when you can't," he said.

Kennedy was in Texas, where his wife grew up, to campaign for another young House Democrat, Rep. Beto O'Rourke, who is challenging GOP Sen. Ted Cruz. O'Rourke told him that on a recent campaign trip to a small town, he was told no Democrat had campaigned there for 40 years. Kennedy stressed to CNN that fellow Democrats need to prove they mean it when they say every voice, every vote counts. "That's how you start to earn people back. You show up."

He thinks leaders from both parties need to get a "little bit outside those comfort zones, outside the district and actually try and listen to some of those voices that are coming from places that we don't represent because those voices count too. And I think if you zoom out far enough at that moment you've got an electorate writ large which is really angry at Washington that just isn't listening."

***

It's rare that a top House Republican leader agrees to sit down to talk to a reporter working on a story about a junior House Democrat.

But House Majority Leader Kevin McCarthy has a struck up a close friendship with Kennedy, bonding over early morning workouts in the House gym where they talk about politics and family. The California Republican is sometimes as effusive as Democrats in praising Kennedy.

"I think he's got more potential than anybody else on the Democrat side of that conference because of the way he carries himself, the homework that he does and his ability to serve," McCarthy told CNN recently in an interview in his Capitol office.

The No. 2 House GOP leader travels to Massachusetts regularly to raise money for his party, but says when he's "off the clock," he spends time with Kennedy and his wife, Lauren.

When Kennedy's wife gave birth to their daughter, Ellie, McCarthy and his wife delivered a stuffed elephant rocker as a gift.

"So, I jokingly tell Joe Ellie is going to be the first Republican Kennedy," McCarthy says, laughing, and proudly recounting how he posed for a picture with her on a visit to the Capitol.

Though Kennedy, 37, comes from one of the most prominent families in American politics, his colleagues say you wouldn't know it. Illinois Democratic Rep. Cheri Bustos, who invited Kennedy to Chicago last year for a fundraiser, noted a slew of family members who were nationally known figures in the room but says Kennedy is a "policy scholar" and "not a show off."

Kennedy is a draw on the fundraising circuit. He's raised roughly $1.3 million this election cycle so far, according to a source in his political operation, and was tapped to help recruit new challengers, particularly those his age and those weighing a run who also have young families.

Hoyer, who served in Congress alongside Kennedy's father Joe and is close to many in the political family, said "I think his son is as comfortable in his own skin as anybody."

McCarthy spoke less about his name and more about his style.

"He's a very worthy adversary. He's smart. He does that homework and what I really admire about him, he can go out and be one of these legislators who can just go get press," McCarthy said. "That's not his way. He really got the legislator quality of where the Kennedys were in the past."

Before being heavily recruited to run for the seat of retiring Massachusetts Rep. Barney Frank, Kennedy worked as a prosecutor. Several colleagues mention he takes a methodical approach to legislation he pushes in Congress.

"He dives in on it. He treats it like a case," said Oklahoma Rep. Markwayne Mullin, a Republican who serves with Kennedy on the Energy and Commerce Committee, who has also become a close friend.

"He's this tall, redheaded ugly guy that we just seem to get along from day one," Mullin said. "One thing about Joe: Joe's heart is in the right place. I tell him he voted wrong all the time. He tells me he votes wrong all the time. But I know where his heart is and he truly has a passion to serve. You can see that in him."

When asked during an interview with CNN about his family's influence on his approach to congressional work, Kennedy slowed down and paused deliberately.

I am, not surprising, very proud the contributions of many of my family members

"I am, not surprising, very proud the contributions of many of my family members have done, whether it's made to the country, whether in elected office or otherwise," Kennedy said. But then he made clear he's cutting his own path, saying "I'm also conscious of the fact that if you are in, serve in elective office, that by far the most important thing that you have is your credibility."

The issue of credibility comes up again when he talks about the task ahead for a party rebuilding after a stunning national defeat in 2016 but is sensing renewed energy heading into the midterms.

"I think what (the 2016) election showed is we've got to do a better job of recognizing that it's not just, it's not just spewing out various policies, even if you might be right on the policy," he said. "You have to have the credibility to be able to talk to someone and say, 'listen, this is why I think this is going to be best, help your family, help your future,' and that is a credibility that has to be earned, not just granted."

Mullin tells CNN the first serious policy discussion he had with Kennedy when they started together in the House in 2013 was about health care. He remembers how passionate Kennedy became, telling him then that the issue was something his family championed in Congress for 50 years.

And that issue earned Kennedy national attention during the health care debate when he delivered an emotional speech that went viral. During a marathon committee markup on the GOP's Obamacare repeal and replace bill, Kennedy ripped House Speaker Paul Ryan personally. He took issue with the fellow Catholic's interpretation of the scripture and calling the measure an "act of mercy." Kennedy denounced the proposal to repeal and replace Obamcare as an "act of malice."

When asked about the role younger members can play, Kennedy won't criticize Pelosi, calling her "one tough lady and one tough leader." And he cautions against pigeon-holing someone because of their age.

"We have to be disciplined enough not to prejudge because somebody is an older socialist from Vermont, that they can't necessarily speak to the hopes and aspirations of a coal miner, a farmer, a college student, a millennial that loves avocado toast," Kennedy said.

***

Even before he arrived on Capitol Hill, Moulton was a party renegade. In the 2014 midterms, he challenged Rep. John Tierney, an 18-year veteran backed by Pelosi.

He gained national headlines for being the first to oust an incumbent that election cycle, and again in 2016 when he publicly called for Pelosi to step down from leadership to make way for newer Democrats to chart the party's future. He backed Ohio Rep. Tim Ryan's challenge to Pelosi's status as minority leader. He notes that while Ryan failed in that effort, he still got 63 votes in the secret election. Of those, only Moulton and roughly a dozen others have gone public.

Hoyer, who years ago had his own leadership battles with Pelosi, said Moulton's moves remind him of himself. Before he came to Congress, Hoyer was the youngest president of the Maryland state Senate.

"I'm not so old that I can't remember being a Young Turk myself," Hoyer told CNN, adding about Moulton, "he's sees himself as an agent of change."

Hoyer works closely with Pelosi now. But he praises Moulton as "very bright, very energetic" and a top messenger on national security issues. Moulton's military service comes up a lot in an interview in his Longworth office in between votes recently. It's what he says exposed him to people from all walks of life and economic levels, and instilled a desire to continue in public life after his four combat tours in Iraq.

My battalion motto in the Marines was 'whatever it takes' and I'm going to do whatever it takes to help win back the House in 2018

"My battalion motto in the Marines was 'whatever it takes,' and I'm going to do whatever it takes to help win back the House in 2018," Moulton told CNN.

He was recently tapped, along with California Democratic Rep. Jimmy Panetta and Florida Democratic Rep. Stephanie Murphy, to head a task force to educate House Democrats about foreign policy and defense issues.

"That's a sign that he wants to be a deep thinker and wants to be a big player. And I think it was smart for him to do something like that," Bustos said.

The Illinois Democrat was part of the trio -- along with Moulton and Ryan -- invited to headline the annual "steak fry" fundraiser in Iowa in September. She said she values his counsel on defense issues, but acknowledged that his tactics inside the caucus, such as his challenge of Pelosi, have caused some friction.

"People who talk publicly about leadership and the need for leadership change, that's going to ruffle some feathers," Bustos said.

While Moulton, 39, may criticize Pelosi, he is doing the same thing she did to propel her stock among her colleagues: Raising big bucks for fellow Democrats as they prep for the next election.

He created his own political operation that recruits and mentors candidates who served in the military or have service backgrounds. He says he saw a hole and decided to take on a veterans' candidate program, and he worked with an outside group, VoteVets, to partner with the Democratic Congressional Campaign Committee to ensure these types of candidates were getting attention.

Moulton's colleagues have taken notice of the impressive $600,000 he's raised, plus $300,000 for his own re-election campaign.

He told CNN his goal is to formally recruit and back two dozen veterans through his political group -- the same number Democrats need to win back control of the House.

Democratic Rep. Ben Ray Lujan, who heads the DCCC, praised Moulton for zeroing in on the need to focus on fellow veterans.

"He has brought in a spirit of he's willing to speak up and stand up and say what needs to be said based on what he believes, that is in the best interests of his constituents and the people he is fighting for," Lujan said.

Moulton's speech in Iowa earlier this fall didn't hold back on the challenge facing his party. He said while Americans in communities across the country were struggling economically, Democrats were "in the worst position since the 1920s to do anything about it."

He pointed to losses both at the national and local level and used them as evidence of his central theme: "That means that we've got change to make. That means that we can't just keep doing the same old thing and expect to win again. We've got to get back to our party roots. We've got to get back in touch with those voters that we have lost, because the reality is that a lot of Americans feel left behind -- not just by the Republicans, but by our party, and by our country."

In his Washington office, Moulton says part of the reason he's helping bring candidates in and support them is because he's worried other Democrats aren't creating the environment to foster more people to get engaged in politics.

"I think there is a lot of chaos right now and that's a sign that there's a leadership vacuum," he said.

He said he doesn't pretend to have all the answers, but says the focus on veterans is his "niche." While he offers his own take on the kinds of issues and economic message he believes is important he says it's too early to be telling voters what matters in the next election.

"We need to be in listening mode for our party right now as Democrats, not in preaching mode," he said.

Asked about the congressional Democrats' recent roll out of a message campaign offering voters "a better deal," Moulton again breaks with his own leadership.

"A better deal sounds like we're talking about the same deal that everybody has today and we're just going to make it better," he said. "The economy is changing too fast for that. We need to be talking about the future, that's part of why I'm talking about a new generation of leadership and recruiting all these young people to run for Congress."

He says he's working with the DCCC and his own effort to flip more red seats in the House, but adds, "We've got to have a message, we've got to have a vision and it's going to be hard to win if we don't have new leadership."

Not surprisingly, Lujan, a close ally of Pelosi's, disagrees with Moulton's criticism of the top House Democrat. And he appeared to issue what might be a warning to Moulton about any additional effort to push her out.

"You need to be able to learn to count to get there and I think that is a skill set that more people need to fully appreciate and clearly leader Pelosi has understood the importance of counting, if you will. Not just to get bills passed, but with leadership votes as well," Lujan told CNN.

Drew Hammill, Pelosi's spokesperson, accused Moulton of grandstanding.

"Leader Pelosi enjoys widespread support in the House Democratic Caucus," Hammill told CNN in a statement. "The few who take potshots in order to get booked on TV are merely a distraction from the goal of retaking the House majority. Leader Pelosi will not be deterred from her mission of winning the House back for the American people."

Moulton appeared annoyed when pressed on whether he's taken on Pelosi to garner more attention for his own political profile and says he's not getting any blowback from colleagues.

"The number of Pelosi allies who have come to me and told me to back off, that I'm not doing the right thing is exactly zero," he says, adding, "the number of members of the caucus who voted for her, who have checked to see who was listening and then patted me on the back and then said 'keep going Seth, you're doing the right thing' is literally dozens."

Like Kennedy, Moulton has also collaborated with Republicans in the House. After the Las Vegas shooting that killed 58 and injured hundreds, he teamed up with Florida Republican Rep. Carlos Curbelo on legislation to ban bump stocks, the accessories that can convert a firearm into an automatic weapon.

Even though there was a similar bill offered by top House Democrats, he decided to get behind the version with Curbelo. "I just think it's the only realistic way to do anything when you are in the minority," Moulton said.

Oklahoma GOP Rep. Steve Russell, also a veteran of Iraq and Afghanistan, has traveled overseas with Moulton. Russell told CNN their politics are polar opposite but they share a "warrior bond."

The two created the "warrior caucus" a group of roughly 30 House members who served in combat, and try to find military readiness issues to work on together.

"One of the things that I like about Seth is that he is intellectually honest, he won't retreat to a partisan corner as a matter of course," Russell said. "He may not commit to something without further study, but he's willing to engage and dialogue."

***

As with any up-and-coming politician, the conversation about Moulton and Kennedy quickly turns to the future.

Moulton made clear he didn't want to talk about any political positions in the years to come.

"I think it's a huge mistake for people in the party to be thinking about 2020," he said. "If we can't figure out how to win in 2018, we're going to be a mess in 2020."

When asked about taking a run at a top leadership post in the House after the midterms, Moulton says, "I'm not going to write it off, but it's truly not what I'm thinking about."

The former Marine grew noticeably irritated when pressed about prospects for a Senate bid if one of his colleagues retires or runs for another office, or whether his Iowa trip or work on a new book about public service are precursors for a national campaign down the line. He says he was invited to Iowa because the organizers of the annual event were looking for "people who are trying to breathe new life into the party." But he said spent the bulk of his time at the event "with a Miller Lite in one hand and an open hand to meet more people."

Meanwhile, former Rep. Patrick Kennedy believes his cousin has the credentials to move up if he decides he wants a career beyond the House.

"There's just no question that if he sticks to doing what he's doing now that every one of the options that have been mentioned that are not only a possibility, but a reality," he said.

Joe Kennedy shrugs off questions about whether he has designs beyond his current House seat.

"If a Senate seat were to come open, yeah it's something I'd take a look at," he said.

But he also says it's not just him who will decide. His family is growing after his wife had a second child just before Christmas.

"I'm young I've got a young family and it's a great family and as other opportunities come up, I'll take a look at some of those when they do but it's got to be right for my family and for me at the time," he said.

This story has been updated.