Republican Sen. Joni Ernst of Iowa on Saturday kicked off what could be a hard-fought re-election campaign as Democrats eye the perennial swing state. The freshman senator urged an enthusiastic crowd that she needs their support to help "stamp out socialism," citing policy proposals from some of the Democratic presidential candidates.

"We can't take our way of life for granted because the very values that make up the heart and the soul of our state are under attack," Ernst said. "The radical left will stop at nothing until socialism has spread from coast to coast."

The junior senator from Iowa announced her re-election campaign at her signature Roast and Ride event with several hundred supporters attending. Ernst began the day by leading about 250 motorcycle riders on a 49-mile journey from Des Moines to Boone. Some supporters honked as she passed by and one man waved a large American flag as she rode by him.

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Ernst won 53% of the vote in 2014 for retiring Democrat Tom Harkin's seat, and Democrats are hoping to take the seat back, especially as President Trump's tariffs have hit the state hard. Ernst already has at least three Democrats challenging her: Theresa Greenfield, who ran unsuccessfully for Congress in 2018 and is president of a real estate company, business owner Eddie Mauro and attorney Kimberly Graham. Democrats need to pick up four seats in 2020 to regain majority control of the Senate, but Ernst vowed she'll be returning to Washington.

"I know that this is an important seat that the Democrats would love to have back," Ernst told reporters. "I am going to make them fight for it and they are going to fail. I am going to hold this seat."

Ernst highlighted a relationship with Mr. Trump, saying he's always welcome to campaign in Iowa, a state he won in 2016. Despite linking herself to some of the president's policies like border security and appointing conservative judges, Ernst said she's not afraid to push back on issues where they disagree, including tariffs.

"I've talked to the president, he knows that I'm not necessarily a tariff gal, but he will tell me, 'well I'm a tariff guy,'" Ernst said. She added that she's spoken to farmers in Iowa who are "okay with his stance on China."

In a statement, Iowa Democratic Party Chair Troy Price criticized Ernst's record in Washington, including her votes for Mr. Trump's tax cut and to repeal the Affordable Care Act.

"Iowans won't forget Ernst's broken promises and Democrats are building a ground game to make sure voters know the truth about Ernst's record of putting political ambitions above the best interests of the Hawkeye State," Price said.

Ernst brought out some of her supporters, including her fellow senator from Iowa, Chuck Grassley, Gov. Kim Reynolds and former U.S. ambassador to the United Nations Nikki Haley. Haley went after the 2020 Democratic presidentials contenders, who have been campaigned heavily due to Iowa's first-in-the-nation contest, calling them "a really odd collection of liberals, radicals and socialists."

"And I know a lot about liberals, radicals and socialists. In case you forgot, I used to work at the United Nations," Haley said. She continued her jabs at the U.N., calling it an "unusual place" due to the criticism the U.S. sometimes faces from other members.

"Nowhere else in the country can you hear America being denounced in 10 different languages at the same time, unless of course you're at any of our college campuses," Haley said.

Republicans at the Roast and Ride echoed the statements from Ernst and Haley that the Democratic Party, and its presidential candidates, are moving too far left.

"There is a sense of radicalism and left-leaning opinions from the majority of the (presidential) campaigns," said Randy Weisheit, a small business owner from Ankeny, Iowa.

"I think it's going away from what the country was founded on," said Darryl Jessen, from Iowa Falls.

Some Democrats have chosen to embrace the "socialism" label, with a 2018 Gallup poll found 37% of Americans viewed socialism favorably, up two points from 2016. And this week, Sen. Bernie Sanders of Vermont, who has been polling in second place, defended what he calls "democratic socialism." Republicans at Ernst's event criticized some of the policies he supports, including Medicare for All and free public college.

Others candidates, such as former Colorado Gov. John Hickenlooper and former U.S. Rep. John Delaney, have cautioned against embracing socialism.

Ernst also said she's working to complete another tour of Iowa's 99 counties. It would be her fifth time doing so and she says it helps her keep a relationship with her constituents.

"Every Iowan has a voice that deserves to be heard," Ernst said. "How can you push for the needs of the communities in your state when you don't travel across your state and hear straight from those folks?"