When Colorado voters cast ballots in the upcoming primary election, they’ll almost certainly face a smorgasbord of candidates spread across an unusually high number of races up and down the ballot.

And for the first time, the state’s unaffiliated voters – there are slightly more of them than there are either Democrats or Republicans – will have a say in the outcome.

The number of major candidates running to replace term-limited Gov. John Hickenlooper is approaching double digits, with as many as four or five likely to qualify for each major party’s primary ballot. There are also crowded races for state treasurer in both parties and for attorney general among the Democrats, as well as what’s shaping up to be primaries in every one of the state’s seven congressional districts. Throw in a smattering of contests in legislative and other races, and most primary voters will be facing more choices than ever before.

In the wake of the 2016 passage of Proposition 108, a ballot measure allowing unaffiliated voters to vote in either the Republican or Democratic primary without having to join either party, politicians and election officials are preparing for an influx of new voters in what have always been partisan affairs.

Pundits, pollsters and political consultants say common perceptions about unaffiliated voters tend to be mistaken – and that those voters’ participation in the election could influence the results in ways different than anticipated.

“It’s the political gold rush of 2018,” says Josh Penry, a principle with EIS Solutions and a former Republican Senate leader from Mesa County. “There’s gold in those hills.”

“We’re in new territory. This is the first time the Democrats have had a complete blowout hootenanny in a long, long while,” says pollster Floyd Ciruli, alluding to all the contested races in the Democratic primary.

“The Republicans are apoplectic too. This is a heavy-duty election. Everyone’s going to be working the unaffiliateds,” says Ciruli, who’s been keeping tabs on the opinion of Colorado voters for decades.

Starting in early June, Republicans will get a Republican primary ballot in the mail, and Democrats will get a Democratic primary ballot, but most unaffiliated voters will get one of each and have the opportunity to pick which one to fill out and return by the June 26 deadline. (Unaffiliated voters can request in advance to receive just one party’s, though it’s unknown how many will.)

As far as the mechanics go, county clerks will be paying more to print, deliver and process roughly 50 percent more ballots than in previous primaries. The secretary of state’s office plans to mount a highly targeted advertising campaign starting next month to educate unaffiliated voters – particularly to encourage them to mark and turn in just one ballot, because if they vote them both, neither will count.

Keeping that number down could be critical, election observers say, pointing out that roughly 7 percent of unaffiliated voters didn’t have their votes counted in Washington the first time that state held its open primary – potentially more votes than the margin in some close, crowded races in Colorado this year.

According to recent polling conducted for the secretary of state, 45 percent of unaffiliated voters said they know they can participate in the 2018 primary election, compared to 47 percent who didn’t know, with voters under age 34 much more likely to be aware than older voters. In all, 39 percent said they intend to vote in the primary, 28 percent were undecided and 33 percent said they won’t.

At the end of January, Colorado counted 3,219,953 active, registered voters – 1,163,751 of them unaffiliated, 1,003,424 Democrats and 995,090 Republicans, with the remainder belonging to minor parties. The ranks of unaffiliated voters have been growing at a significantly faster clip than either major parties’ for some time.

While there are clear demographic and geographic differences between the two major parties as a whole – Republicans tend to be older, whiter, more likely to be male and less likely to live in urban cores, with Democrats tending the other direction – it’s harder to characterize unaffiliated voters in Colorado, according to voter registration and polling data.

“The archetype of the independent voter is changing rapidly,” Penry says. “The really crude stereotype was that they’re less politically engaged, moderate and busy living their lives, that they don’t really like this politics thing but cast a vote every presidential election. But there is a huge block of independent voters as animated as any partisan, and they’re animated by disgust with partisans.”

Jason Bertolacci, a spokesman for Let Colorado Vote, the group behind Proposition 108, has been working with the secretary of state to implement the new law.

“Just because they aren’t engaged in a party doesn’t mean they don’t want to have an impact on elections,” he says. “It’s not like the parties have a lock on the principle of engaged voters.”

While polling shows that roughly half of unaffiliated voters identify themselves as moderates, political pros say it’s a misconception that unaffiliated voters constitute an “inert,” middle-of-the-road bloc occupying the space between the two parties. As likely as not, they feel the GOP isn’t conservative enough for them, or they share progressive values with the Democrats but are disinclined to identify with a party. Those will be the most likely voters to participate in the primaries.

“The unaffiliated voter is not necessarily a moderate – in many cases it’s more liberal or more conservative than even the typical partisan,” Ciruli says.

In other states that hold open primaries, he noted, unaffiliated voters often amp things up rather than moderate the outcome.

“When they have been involved, it’s been sending a message or voting for a celebrity type of politician – a Bernie Sanders, a Donald Trump fit that category and attracted them,” Ciruli said.

After former U.S. Rep. Tom Tancredo’s departure from the GOP gubernatorial primary last week, Ciruli added, Colorado’s primary might not have that kind of choice on either ballot.

Ciruli and Democratic pollster Chris Keating of Keating Research both discounted suggestions that some unaffiliated voters might cast their votes strategically – a progressive-leaning voter voting for a weaker candidate in the Republican primary, for instance – particularly because both parties have hotly contested races at the top of the ticket and on down.

“Unaffiliated voters in general want someone willing to work together to get things done, but that doesn’t mean they have some kind of strategic play,” Keating said. “Most of them have more important things in their lives than worrying about politics.”

Keating said he’s found substantially higher levels of enthusiasm among Democratic voters this year than he’s ever seen, potentially diluting the effects of the unaffiliated turnout in that party’s primary.

“Democrats are significantly more interested in voting in the 2018 election than Republicans. If they’re more interested in voting in November, there’s going to be a Democratic surge in the primary, which might push down the effect of unaffiliated voters,” Keating said.

In 2010, the last year there were major, statewide contests in both parties’ primaries, about 410,000 Republicans and about 340,000 Democrats cast ballots.

Among states that have opened up their primaries, Colorado is rather late to the game, so there are plenty of examples to consider, but a unique combination of factors – and an election year that’s looking like no other – make it hard to find strict comparisons.

Colorado will be the first state with all-mail ballots to hold an open or, more accurately, a semi-open primary (the distinction being that an open primary allows anyone to vote in any primary, as opposed to just unaffiliated voters being able to participate), which could skew turnout predictions.

“Unaffiliated voters are going to have that ballot show up in their mailbox,” says Bertolacci, the Let Colorado Vote spokesman. “It’s going to be a very easy step for them to participate, and probably not a big step for a smart candidate to chase those ballots.”

Although younger unaffiliated voters say they plan to vote at higher rates than their older counterparts, older voters tend to return their mail ballots more often, potentially muddying that distinction.

“All the campaigns are spending a lot of time thinking about how to unlock some share of that voter bloc. It is a totally new frontier and it’s a huge opportunity for these campaigns,” Penry says. “The combination of the new law and mail ballots together has a compounding effect and will tend to favor the smartest, best-funded campaigns.”

While nearly every campaign will say it’s going after the unaffiliated newcomers to the primary, only the most sophisticated and well-financed campaigns will be able to accomplish that, he maintains – but for them it could make all the difference.

“Voter modeling and data is so good these days that the top-tier campaigns already have a pretty good sense, almost certainly, which independent voters have a pretty good chance of turning out. The targeting will matter, but it will favor candidates with enough resources to reach into this massive new pot of voters. The data and the modeling and the basic know-how of these high-level campaigns is so high, they’ll be able to systematically execute a program targeted at independent voters this year.

“How much will it matter? This is all margin. These are all new votes. These are highly fragmented primaries at the top of the ticket. If you get super-sophisticated about 15,000, say, or 25,000 new houses – maybe you’re the only one talking to them – in a race that could be decided by a 30-percent plurality, it’s going to have a huge impact, there’s no doubt about it.”