Transcript for Bernie Sanders on what it'll take for a 'blue wave' to hit Congress

Reporter: Maybe the junior senator from Vermont. If I were a Republican looking out at this crowd, I would be very nervous. Reporter: For this crowd here in Wisconsin, he's a rock star. Senator Bernie Sanders has been making the rounds in lots of states ahead of the midterms. It looks to me like Oceanside is ready for a political revolution. Reporter: The white hair, the rumpled suit, and that unmistakable accent. I'm here today to end one party rule in Washington. Reporter: A gentle reminder of what might have been and maybe, just maybe, could be still. Got a lively crowd here. Oh, yeah. Reporter: Backstage in Kenosha, talking strategy with Illinois congressional candidate Garcia, Sanders down plays the idea of a big blue wave. Anybody thinks this is going to be easy, the Democrats are going to end up with a 20-vote majority, is absolutely dead wrong. The Republicans can still hang on. They can still win this thing. Reporter: He's doing everything in his power to get out the vote. The Kenosha venue is a uaw hall, blue-collar voters one and all. What is it that Bernie Sanders brings to the table when it comes to an event like this? Excitement and vision for the future. Reporter: Voters here fit the same profile as the ones that helped Donald Trump win Wisconsin on the promise of America first. You don't see me with a hat on me that says make America whatever again. Reporter: They're all for protecting the steel industry, bringing back manufacturing jobs and helping America's farmers. They're just not for trump. No, we're not coming in as a blue wave. We're coming in as a blue tidal wave. Reporter: Tidal wave. As Bernie Sanders himself says, it all depends on the turnout. In 2014, we had the lowest voter turnout in modern American history. In 2018, with your help, we're going to have the highest voter turnout. Reporter: Sanders has never really stopped campaigning since 2016. Hello. Reporter: The quixotic campaign he launched for the presidency, tilting at windmills, ended up gathering an astonishing head of steam. Now Bernie's campaign has become a movement. Here's the radical idea. Are you ready? Here it comes. Maybe, just maybe, we should have a government that represents the needs of the middle class and working people of this country and not just wealthy campaign contributors. There you go. I know it's a radical statement. Hey, I'm going to stick to it. Reporter: Remember all those small dollar donations Sanders used to talk about during the 2016 campaign? And you know what that average contribution was? $27. Reporter: Turns out there was a lot of money left over, most of it rolled over into our revolution, a political action committee fielding some 200 Progressive candidates for state and local office. In the past few weeks, Sanders has criss crossed the country, ginning up support in 11 states, hoping he'll soon have some company on capitol hill. So in Indiana. We're going to come together and elect Liz Watson as the next congressperson. Reporter: In Colorado, states where he beat Hillary Clinton in 2016. Joe, your next member of the United States congress. Reporter: In Nevada. I'm here today to help elect Jackie to be the next united States senator from the great state of Nevada. Reporter: Finally, this week, in Florida. Your job is to elect Andrew Gillum. Your job is to have the highest voter turnout for a midterm election in Florida history. Around the country, there is a new generation of Bernie Sanders style candidates running, and even in red parts of the country, they want him to come campaign for them. Reporter: All told, since the 2016 election, he's visited 30 states. You have certainly made a dent in the democratic party. Now it seems like you're trying to make a real difference with a slate of candidates across the country for everything from the senate down to local elections. Who are you most excited about in that crowd? Well, we have great candidates. Reporter: Democratic Randy Bryce is running in Wisconsin's first congressional district, the seat currently held by house speaker Paul Ryan. When you entered this race, I gather you were a bit of a sacrificeal lamb, you were the long shot and suddenly you're the front runner We've been able to put together something that hasn't been put together in the 20 years that Paul Ryan has been here. Reporter: Bryce is an iron worker by trade and a former volunteer on Bernie's 2016 campaign. I've heard they call you iron stache. I've been called that. Reporter: And I also read that your campaign not only supports unions but is unionized. We're the first in American politics to unionize, absolutely. With your help and with help from people all across this country, we were able to repeal Paul Ryan. All over this country, people like Randy who were never really involved in electoral politics before, you're seeing that. Young people, people of color, women, suddenly they are running for office and they are winning. So I think come November 6th, Washington, D.C., is going to be in for a big surprise. Reporter: The pendulum has swung to the right. There's no question about I. And I see that you want to swing it to the left. There are those who would say in a polarized, divided country, we ought to find common ground in the middle. Yeah, I think that's right and I think if you look at the issues that we're talking about, that is the common ground. And the American people very strongly want a government that represents them and not just the 1%. Reporter: So you're redefining the middle. Yeah. And it's not just me. Look at the polling. All these things that I'm telling you, that's what the American people want. Sanders points to the success of candidates like Alexandria ocasoi-cortez in Brooklyn, a young Progressive, now at age 29, poised to become the youngest member of congress, and he'd be the only democratic socialist in the house. Reporter: The issue is not just November 6th but also 2020. Does the democratic party have the bench needed to take trump? I think there are a lot of people out there who have experience, who have knowledge and who are prepared to take on the big money interests who dominate our economy and our political life. Reporter: Including Bernie Sanders? Well, I'm now focused on 2018. I'm working as hard as I can. Reporter: So he's not ruling it out. He's hiring back a lot of his old staff. He's starting to fund raise for himself and keep money in a war chest. He's going back to those early important states like Iowa and Nevada and New Hampshire. Reporter: But in 2020, he'll be 79, 9 years older than Donald Trump was when he took the oath of office, the oldest man ever elected president. There are folks, forgive me, who say Sanders, Biden, even Clinton, getting a bit long in the tooth. Time for fresh faces. I think what the media should be focusing on are the issues impacting the American people and the political leadership will follow that. Reporter: First things first, Sanders insists. There will be plenty of time to discuss that after the midterms. I'm David Wright for "Nightline" in Kenosha, Wisconsin.

This transcript has been automatically generated and may not be 100% accurate.