U.S. Sen. Jeff Merkley (left) canvassed in Fort Mill on Saturday with South Carolina Statehouse candidate John Kraljevich. The Oregon Democrat returned to the Palmetto State for his second visit in recent months as he continues to lay the groundwork for a potential presidential bid in 2020. Provided/John Kraljevich

COLUMBIA — U.S. Sen. Jeff Merkley, D-Ore., returned to South Carolina this weekend for his second visit to this early presidential primary state as he continues to lay the groundwork for a potential White House bid in 2020.

On Friday, Merkley held an environmental roundtable in Charleston and met with local officials before driving to Columbia to participate in a town hall hosted by the South Carolina chapter of Our Revolution, a progressive political organization launched by U.S. Sen. Bernie Sanders after his 2016 presidential campaign.

Then on Saturday, Merkley spoke at a Democratic candidate training in Rock Hill and spent a couple hours canvassing with John Kraljevich, a Statehouse candidate from Fort Mill. He ended the South Carolina trip by attending U.S. Rep. Jim Clyburn's annual scholarship banquet in Santee on Saturday night. 

Merkley is among several Democratic 2020 contenders who have swung through South Carolina in recent months to begin making connections with a primary about 18 months away.

Los Angeles Mayor Eric Garcetti toured parts of the state in February and has since hosted a fundraiser for South Carolina Democrats that brought in $100,000. New Orleans Mayor Mitch Landrieu and California U.S. Rep. Adam Schiff spoke at a party conference in December. Maryland U.S. Rep. John Delaney, the only Democrat who has already launched his 2020 campaign, has visited the state multiple times.

Former Vice President Joe Biden, who maintains many longtime ties to the state, spoke at the Charleston NAACP in February and has remained active in South Carolina politics by endorsing Democrat James Smith for governor and more recently, state Senate candidate Dick Harpootlian.

But Merkley is the only White House prospect from the party's more progressive wing to visit South Carolina.

The only senator to endorse Sanders' 2016 presidential bid has been candid about his presidential aspirations in recent months, saying he is "exploring the possibility" of a bid — even if some of his ideological allies like Sens. Sanders and Elizabeth Warren launch their own campaigns.

Merkley told The Post and Courier he plans to make a decision after the November midterm elections. But in the meantime, the senator first elected in 2008 has been building the types of relationships that could prove vital in a primary field that is expected to be very crowded.

"My main mission here has been to travel the states and help them build their parties," Merkley said. "People are working to build a blue wave under challenging conditions. ... There's a sense of a lot of work to be done if we want to reclaim our nation."

He cast the upcoming South Carolina governor's race between Democrat Smith and incumbent Republican Gov. Henry McMaster as an opportunity for the party to "contrast the vision of the working people of the state with the rich and powerful and privileged."

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Sen. Jeff Merkley, D-Ore. speaks to reporters just outside the Senate chamber on Capitol Hill in Washington, Wednesday, April 5, 2017. The senator returned to South Carolina for the second time in recent months this weekend to continue laying the groundwork for a potential presidential bid in 2020. (File/AP Photo/J. Scott Applewhite)

In the 2016 Democratic presidential primary, Sanders struggled to keep up with Hillary Clinton in many southern states, including South Carolina, where he got just 26 percent of the primary vote.

But Merkley attributed that in large part to Clinton's longstanding relationships throughout the South and argued that a progressive candidate who calls for higher wages, universal health care, improving public schools and making college more affordable can perform well.

"I think those fundamental ideas resonate very well with working families throughout the South," Merkley said.

Merkley first visited the Palmetto State in April when he delivered the keynote address at the state Democratic Party's annual convention in Columbia.

Sam Edwards, a Statehouse candidate from Irmo who attended the Our Revolution SC town hall over the weekend, said she has been impressed by Merkley's outreach to grassroots organizers and activists.

"As an activist, you don't get a lot of down-to-earth politicians wanting to hear from you and talk in a circle for any extended period of time, and that's what Jeff Merkley's done twice here," Edwards said.

More potential candidates are expected to visit South Carolina in the coming months, particularly after the midterm elections.

But by making repeat stops in South Carolina early, local Democrats said Merkley can leave a positive first impression that will come back to help if he does end up deciding to run.

"He's very good at developing relationships and I think that's smart politics because when he comes back next, these South Carolina organizers and people who are active in their community will be able to say, 'My friend Jeff's here,' not just some presidential contender," Kraljevich said. "I think that's really powerful."

Follow Jamie Lovegrove on Twitter @jslovegrove.

Jamie Lovegrove is a political reporter covering the South Carolina statehouse and congressional delegation. He previously covered Texas politics in Washington for The Dallas Morning News and in Austin for the Texas Tribune.