SEATTLE — Bartenders at Elysian Brewery didn’t need to mix green dye in the beer to make last weekend’s pregame scene more festive.

Hundreds of Sounders FC fans, some with “rave green” jerseys on their chests and others with paint on their faces, had gathered at the downtown craft beer joint hours before a Major League Soccer match.

As some fans imbibed, thousands of diehard members of the Emerald City Supporters club made their routine march down the street to CenturyLink Field. At the party, the first-place Sounders beat the Houston Dynamo 2-0 before 50,276 fans.

As two groups wrangle to bring an MLS franchise to Minnesota, Seattle is a prime model of how a soccer fan base — and in particular, a unique fan club — can boost a bid.

Members from both Minnesota groups — the Vikings as well as United FC, the existing pro team in the second-tier North American Soccer League — were in Portland for the MLS All-Star Game on Aug. 6.

Those groups and competitors from about six other cities are vying for the 24th and final expansion franchise to be awarded before 2020.

“We want to have 24 teams by the end of the decade, so we certainly have some time to make that decision,” said MLS spokesman Dan Courtemanche. “We don’t want to set a hard deadline because it’s six years away.”

In Portland, the prospective ownership groups met with existing MLS owners and a likely topic of conversation was “supporters groups.”

Courtemanche said the league is looking for three things from the eventually successful expansion bid: an ownership group with financial fortitude; a stadium (or a plan for one); and a dynamic market that can support a franchise.

A “supporters group,” an organically grown collection of rabid fans independent of the team, is a prime example of that third tenet.

On ownership, both the Vikings (Zygi Wilf) and United (Bill McGuire) are formidable.

For the stadium, the Vikings are constructing a nearly $1 billion stadium in downtown Minneapolis, while the United are exploring opportunities for a much cheaper soccer-specific stadium.

The Vikings’ ability to secure a half-billion dollars in public money could impinge on United’s ability to ask municipalities for more. United President Nick Rogers, however, says it’s too early to tell if the coffers are closed.

On the fan base, the United have a distinct advantage over the Vikings.

Before United, a moniker of the pro soccer team was the Thunder, and a dozen or so fans informally set up what would become the Dark Clouds supporters group when home games were held in St. Paul in 2004.

“The joke was that you couldn’t have Thunder without Dark Clouds,” said Bruce McGuire, a supporter since the beginning.

Now, the Dark Clouds are approaching 400 members and descend on two sections in the south end of the National Sports Center in Blaine during home games.

“Like the team on the field (which has a 10-game league unbeaten streak after Saturday’s 5-1 win over Indy Eleven) they have evolved and grown close,” United coach Manny Lagos said. “As a result, we have one of the best supporters groups in the country.”

The Dark Clouds aren’t the largest supporters group, but they make up for their lack of numbers in creativity. They are known for digging up dirt on players — such as one opponent being an underwear model — and using that material for trash talk.

“The MLS brass know exactly who we are,” McGuire said. “They know a lot of us personally. … They see the importance that (supporters groups have) had in other cities.”

A FEW TO THOUSANDS

The Dark Clouds were the ominous presence at Thunder games against the Sounders and Portland Timbers before those clubs made the jump to MLS a few years ago.

“They were some of our biggest adversaries,” McGuire said.

Seattle, which celebrates 40 years of pro soccer this year, joined MLS in 2009. Membership in its main supporters club (ECS) has more than doubled to 5,000 since the move to the top U.S. league, said Aaron Reed, the club’s co-president.

“I think that having that (supporters group) proves to MLS that a market loves the game,” Reed said. “And that it’s scalable and something they can expand on.”

The scales also have been tipped in Portland.

The Timbers, who date back to 1975, were reincarnated in 2000 in the lower-tier leagues and joined MLS in 2011. The Timbers Army supporters group stated in 2001 with “a few hardy souls” and now has at least 6,000 members in Providence Park on game days, said Mike Golub, the Timbers’ president of business operations.

Before last weekend’s match, some fans waited outside the stadium for at least 10 hours. For rivalry games with Seattle, the Army encampment will mark its territory overnight.

Golub looks to supporters groups as soccer’s point of differentiation.

“Other sports rely on top-down entertainment with cheerleaders, all the promotions,” he said. “And those are well and good, but in soccer, the energy and entertainment and passion really comes organically from our supporters groups. It’s one of the things that makes soccer so intoxicating and distinct.”

HARD LESSONS

When MLS started in 1996, it hitched its success to interest from families in the first decade, McGuire said.

“They learned a lot of hard lessons and it cost them a lot of money,” McGuire said. “Families and kids, future soccer players, and the youth leagues: They are vital. But that was the be-all and end-all. They learned the hard way that the diehard fans are the ticket.”

Soccer supporters clubs are influential around the world, and were first realized in MLS with the D.C. United team having a number of strong groups from the start. Then supporters groups picked up with the 2007 expansion of Toronto FC.

“It’s that passion that you see throughout Europe and Latin America that really makes going to a soccer game special,” Courtemanche said. “It’s unlike nearly any other kind of sporting experience.”

Average attendance at MLS games this season is above 19,000, a steady increase over the past five years from about 16,000 in 2009.

Earlier this season, the Sounders led the league in attendance at 40,091, with Portland in the top five at 20,814. The Timbers also have sold out 63 straight home games and boast a season-ticket waiting list of about 10,000.

By contrast, Chivas USA in Los Angeles had the lowest MLS attendance of 7,504, and Minnesota United has averaged about 5,000.

“We need to continue to grow that supporters culture and work closely with them because it’s part of what makes going to an MLS game unique,” Courtemanche said.

HEADS IN THE CLOUDS

Another distinctive element is supporters groups being politically active in bringing clubs to cities.

Both McGuire and Courtemanche credit the Philadelphia supporters group Sons of Ben for its activism in locking in the MLS club, Union, in 2007.

“There would be no MLS team in Philadelphia if it wasn’t for the supporters group,” McGuire said.

In Portland, the Timbers Army flanked its club as it sought $31 million in a public-private agreement for stadium renovations from the Portland City Council in 2010. The MLS’s arrival in Portland was contingent on the deal.

“They helped make our case, and their case, and express to the city and officials how important this would be to the city,” Golub said of a measure that eventually passed 4-1.

The Dark Clouds already are politically active. As the Vikings’ stadium bill was molded from 2010-12, McGuire said members met independently of the club with then-Minneapolis mayor R.T. Rybak.

But the Dark Clouds didn’t conference with the Vikings, McGuire said.

“The biggest disappointment in all that is the Vikings had no time for us,” McGuire said. “They were not interested in what we had to say. It’s ironic now that they are looking to reach out to people that might want to be soccer fans.”

The MLS, however, has paid attention to United matches held at the National Sports Center in Blaine.

“It’s the passion for that club that we’ve seen in NASL regular-season matches,” Courtemanche said, “but also in their recent friendly against (English Premier League team) Swansea City where the crowd (of 9,064) was electric, from what I understand.”

Follow Andy Greder at twitter.com/andygreder.