More than 500 Wisconsin Democrats participated in a presidential straw poll at their state party convention over the weekend, and they sent a powerful signal about the potential of the challenge Vermont Senator Bernie Sanders is mounting to presumed Democratic front-runner Hillary Clinton.

Clinton still maintains a wide lead in national polls and in those from early battleground states such as Iowa and New Hampshire. But the delegates, alternates, and registered guests at the Wisconsin party convention—among the state’s most activist Democrats—gave Sanders 41 percent support to 49 percent for Clinton.

The breakdown of the straw poll vote, which was conducted by the well regarded politics website, was:

Hillary Clinton 252
Bernie Sanders 208
Joe Biden 16
Martin O’Malley 16
Jim Webb 8
Lincoln Chafee 5
No vote 1

Elizabeth Warren 4
Tom Vilsack 1

The senator has been a regular visitor to Wisconsin over the years, as a frequent speaker at the annual “Fighting Bob Fest” gatherings, which draw thousands of Wisconsin activists to outdoor eventseach September. He has lauded the legacy of former Wisconsin US senator Robert M. La Follette, who mounted an independent progressive campaign for the presidency in 1924, and of the democratic socialists who led Milwaukee for much of the 20th century. In recent years, he had worked with Ed Garvey, a former gubernatorial candidate, on a host of issues.

Perhaps most importantly, Sanders is an enthusiastic backer of organized labor—a stance that resonates with Wisconsin activists who, over the past four years, have battled the anti-union initiatives of the administration of Governor Scott Walker.

Clinton has also worked the state over the years. In 2008, she and her backers battled with Barack Obama and his backers in a closely watched February primary. Obama won the primary with a 58-41 margin. But Clinton ran well in many regions of the state and took 32 of the state’s 74 delegates.

This year, at the state convention, Clinton backers were present—with pins and T-shirts. And they were celebrating a recent endorsement of their candidate from Milwaukee Mayor Tom Barrett, a former gubernatorial candidate and 2008 Obama backer.

Sanders supporters were also active at the convention. Members of Progressive Democrats of America, which encouraged Sanders to run, maintained a table featuring a huge “We Want Bernie” banner and handed out Sanders materials. They also held a well-attended meet-up to promote the senator’s bid.

The Clinton campaign, which will formally launch June 13 in New York City, retains huge name-recognition and campaign finance advantages going into the race for the 2016 nomination. A RealClearPolitics average gave her 59 percent support in the race for the Democratic nomination, which in addition to Sanders also includes former Maryland governor O’Malley and former Rhode Island governor Chafee. Former Virginia senator Webb is also considered a likely contender. Other candidates could yet get in, and there are still some folks pushing a bid to draft Elizabeth Warren.

But since Sanders formally launched his campaign late last month with a Burlington, Vermont, event that drew an estimated 5,000 enthusiasts, the senator has attracted large crowds in New Hampshire, Iowa, and Minnesota. Most polls now have him running second to Clinton. A recent Quinnipiac poll had Sanders moving from 4 percent support nationally in early March to 15 percent in late May.

The Wisconsin Democratic Party straw-poll numbers offer a different sort of encouragement for the insurgent campaign Sanders is running.

Last week, in Minnesota, Sanders attracted thousands to a hastily scheduled town hall meeting. The size of the crowd certainly suggested that the senator’s economic-populist message is getting through. At the same time, it offered an indication that Sanders has, through decades of work in Washington and travel around the country, forged a connection with the grassroots activists who are especially engaged with the nominating process in a state that will never get the attention accorded the first-caucus state of Iowa and the first-primary state of New Hampshire—but that will send a substantial bloc of delegates to the July 2016 Democratic National Convention. Now, in another state, Wisconsin, Sanders has gained another sign of unexpected and significant support.