Joe Biden has been holding on as front-runner in the Democratic presidential race, but the former vice president lags most of his leading rivals in building a visible primary campaign in Minnesota, a potential battleground state in November.

Sen. Amy Klobuchar, with campaign headquarters in Minneapolis and backing from most of the state's top Democrats, is staking a flag in her home state ahead of its March 3 primary. The two candidates fighting it out for support from the left, Sens. Bernie Sanders and Elizabeth Warren, also have teams on the ground in Minnesota working to assemble grassroots support.

Former South Bend, Ind., Mayor Pete Buttigieg has motivated a large, active group of volunteers here. Even former New York City Mayor Michael Bloomberg campaigned in Minnesota earlier in January. Sanders, Warren and Buttigieg have all made Minnesota campaign stops this cycle, as well.

By contrast, the Biden campaign's presence in Minnesota has been muted so far. The campaign did recently hire a senior adviser for Minnesota: Corey Day, a former executive director of the Minnesota DFL who said he's started reaching out to potential supporters and strategizing for the upcoming primary. But, with early voting for the primary underway as of Friday, veteran DFL activists said they've yet to see much evidence that Minnesota is a Biden priority.

"I have not seen anything like a demonstrable grassroots push from Biden. I'm not sure what that leaves us to conclude," said Dan McGrath, a political consultant and the former executive director of the progressive organizing group TakeAction Minnesota.

A Biden campaign official told the Star Tribune that Klobuchar's presence in the race is a challenge for Biden's own prospects. Their overlapping political profiles — more moderate on some issues, appeal to swing voters, bipartisan instincts — would suggest that much of Biden's potential support in Minnesota is already on the Klobuchar bandwagon.

Klobuchar's chances in the presidential race depend almost completely on her ability to break through in Iowa's first-in-the-nation caucus, where she has crept up in polls but continues to trail the quartet of Biden, Sanders, Warren and Buttigieg.

The Biden campaign official said that, should Klobuchar be forced out of the race before March 3, when Minnesota votes along with 13 other states, then the campaign would be likely to intensify its efforts here.

Even absent Klobuchar's presence on the ballot, Minnesota's Democratic electorate doesn't closely align with the Biden campaign's strategy. The former vice president's near-universal name recognition from his years serving alongside former President Barack Obama has allowed him to mount more of a national campaign, with a focus on delegate-rich Super Tuesday states like California and Texas, and on the Democratic Party's traditional base of support among black voters.

"Give me a reason why he'd be focusing on Minnesota right now," Steven Schier, a retired Carleton College political science professor, said of Biden. Schier, who has written books about presidential politics, said he doubts Klobuchar is the only factor in the Biden campaign's Minnesota calculations.

"Biden is doing very well with African-American Democrats, and that's not a huge number in Minnesota," Schier said. "Our Democratic electorate tends to be very white, highly educated and liberal, so you can see why Sanders and Warren might see this as more fertile territory."

In fact, beyond Klobuchar — who appeared Friday night at an evening get-out-the-vote rally at the First Avenue nightclub to kick off early voting — it's the Sanders and Warren campaigns that have engaged most actively in Minnesota, with paid staffers who are working on mobilizing grassroots supporters.

"From the Twin Cities to our rural communities, and across all eight congressional districts, our organizers and volunteers are fighting to make big, structural change happen for all Minnesotans," Emily Jensen, the Warren campaign's state director, said in a statement provided to the Star Tribune.

The campaign has some six dozen volunteer "community team leaders" spread out statewide who typically put in five to six hours a week door knocking and working the phones on behalf of the Massachusetts senator's bid. They also have assembled community groups geared to specific interests, including "Artists for Warren" and an LGBT group.

The Sanders campaign has been making similar moves. Reed Millar, the state director, said staffers and volunteers have "made tens of thousands of calls and knocked thousands of doors."

The Vermont senator has also racked up the longest list of Minnesota endorsements after Klobuchar, with backing from U.S. Rep. Ilhan Omar, Attorney General Keith Ellison, and about a dozen state legislators and local elected officials.

Buttigieg's campaign has a paid "Midwest organizing director" based in Minneapolis who's responsible for on-the-ground efforts in several battleground states, including Minnesota. There's also a coterie of about 100 active volunteers who meet regularly to knock on doors and make phone calls.

"A lot of our emphasis is reaching out to people who know and are talking about why we're supporting Pete and why we think they should, too," said Katie McMahon, a professional singer from Minneapolis who's a leader of the group.

For their part, Klobuchar's campaign say they're intent on a strong showing in her home state. Campaign manager Justin Buoen said they've made 250,000 phone calls to Minnesota voters urging them to support Klobuchar in the primary, held multiple events, assembled a long list of prominent backers and built an operation inside the campaign focused on delivering Minnesota.

"We're definitely not taking it for granted," Buoen said.

In early January, the Biden campaign made its first Minnesota hire. Day, who was the DFL's executive director for nearly a decade, said in an interview that he's spent the last few weeks reaching out to community and labor leaders, building volunteer capacity and sending supporters to Iowa to help out there (other campaigns have made the same move with Minnesota supporters).

Rival campaigns "have had a little more time on the ground," Day said. "But we're very aware that early voting is starting, and we're making sure our supporters are aware of it also."

Patrick Condon • 202-662-7452