Now, with King continuing to face controversy -- this time over remarks about rape and incest -- Scholten, with the help of a video narrated by "Field of Dreams" star Kevin Costner, has launched a second bid in the most Republican district in Iowa.
But he faces strong headwinds in a year when President Donald Trump will be at the top of the ticket.
Democrats flipped 40 GOP-held House seats in the 2018 midterms, casting out Republicans in primarily suburban districts around the country -- including two in Iowa -- to take control of the House.
Scholten came remarkably close to unseating King in a rural, agricultural district where Trump defeated Hillary Clinton 60% to 33% in 2016.
"We moved the needle so much last cycle," Scholten told ABC News last week on the sidelines of the Wing Ding Dinner in Clear Lake, Iowa, as the entire Democratic presidential field traveled to his district to woo voters. "We just felt like we ran out of time."
"People want to get out there right away and just, they're ready for change in the district," he said.
King, an immigration hawk and one of the most conservative members of the House, has a history of courting controversy that has prompted backlash from Democrats and, more recently, members of his own party.
This week, the Des Moines Register reported that King, seeking to defend his opposition to rape and incest exceptions in an anti-abortion proposal, recently told a conservative group that humanity might not exist without "rape or incest."
"What if we went back through all the family trees and just pulled out anyone who was a product of rape or incest? Would there be any population of the world left if we did that?" he said last week in a meeting with the Westside Conservative Club in Urbandale, Iowa.
"Considering all the wars and all the rapes and pillages that happened throughout all these different nations, I know that I can't say that I was not a part of a product of that."
Scholten, in a statement, called King's comment "entirely unacceptable," while several 2020 Democratic presidential candidates called on him to resign from Congress, and urged their Twitter followers to contribute to Scholten's campaign.
House Republican leaders, including House Minority Leader Kevin McCarthy and House GOP Conference Chair Liz Cheney, R-Wyo., also condemned King's remarks.
"We have a congressman who's not even on the Agriculture Committee, he got stripped of all his committees, so it's clear, people are frustrated," Scholten told ABC News last week of King's comments.
In January 2019, Republican leaders stripped King of his assignments on the House Judiciary and Agriculture Committees following comments he made to the New York Times about white supremacy.
"White nationalist, white supremacist, Western civilization — how did that language become offensive?" he told the paper in a recorded interview and later disputed.
Following the Pittsburgh synagogue shooting in October of 2018, Rep. Steve Stivers of Ohio, then the chairman of the National Republican Congressional Committee, House Republicans' campaign arm, condemned King, who had recently met with Austrian far-right nationalists on a trip to Europe supported a white nationalist candidate for mayor of Toronto.
It's not clear that Scholten will face King in November of 2020. At least two Republicans – state Sen. Randy Feenstra and Woodbury County Supervisor Jeremy Taylor – have announced primary challenges to King, and Feenstra has significantly outraised the congressman.
Both challengers have condemned King's rhetoric, and warned voters that his nomination could cost the party the heavily Republican seat.
If no candidate reaches 35 percent in the primary next year, the GOP nomination will be selected by delegates at a district convention.
"Only Steve King could make a district that Trump won by over 25% remotely competitive. His racism, misogyny, and homophobia is too much even for some otherwise solid Republican voters," Ian Russell, a Democratic strategist who recently served as the political director of the Democratic Congressional Campaign Committee, told ABC News.
"But it's still a heavy lift for any Democrat, especially with Trump on the ballot - though Scholten will have plenty of resources."
Support for Trump, who will be up for reelection and at the top of the ticket in 2020, remains strong among Republicans in the state, and in a district that has more than 70,000 registered Republicans than Democrats, according to the most recent data from the Iowa secretary of state's office.
"It was out of reach in a Democratic wave year," a Republican official involved in Iowa House races told ABC News about the district. "Republican turnout is going to be at its highest point with President Trump running for reelection."
Without a competitive primary, Scholten is already canvassing his district with the general election in mind – distancing himself from the intraparty Democratic squabbling between progressives and moderates in the House and on the presidential campaign trail.
"People get caught up in national labels. We just believe in getting out there, whether Democrat, Republican or independent, we're out there earning your votes," he told ABC News.
As he ran for president in 2015, Trump repeatedly called King a "great guy," but said "I don't know anything about the situation" regarding King in February, after the congressman was stripped of his committee assignments.
"I read a statement that supposedly he made. I haven't been briefed on it, but certainly it wasn't a very good statement," Trump told reporters on Thursday.
The congressman told constituents he has seen "no signal from Donald Trump that he's anything other than supportive of me," according to the Des Moines Register.
ABC News' Ben Gittleson contributed to this report.