Anyone who has been talking to voters around the country and watching public opinion polls knows that American voters are angry, tired of both political parties, and ready for a change.

Until very recently, though, that frustration has had almost no outlet, as independent candidates for office in the past were rarely competitive and almost always dismissed by the national media as a sideshow.

Not this year.

Suddenly the battle for control of the U.S. Senate appears to hinge on a few independent candidates who won’t say who they will caucus with if they win and are signaling they may not caucus with either party.

In Kansas, independent Greg Orman, a former Democrat who has been stressing fiscal responsibility and problem solving in his campaign, is in an extremely competitive race with longtime Republican Sen. Pat Roberts.

A recent NBC poll showed Orman in the lead. Other polls by Fox and CNN have shown Roberts slightly ahead. Orman got a huge boost in September when Democratic candidate Chad Taylor dropped out of the race after an Orman poll showed he had a better chance of beating Roberts in solidly Republican Kansas.

Roberts and the Republicans are trying to portray the independent as a Barack Obama supporter who is just a Democrat in disguise.

A wealthy private equity investor, Orman is a social moderate and fiscal conservative. He favors entitlement reform and has said on the campaign trail that he has donated money to both Democratic and Republican candidates, including former Massachusetts senator Scott Brown in 2010 because he thought Brown could be the deciding vote against Obamacare, which Orman opposed.

In the past, the candidate has said he would caucus with whichever party is in the majority, but more recently he has been saying he might not caucus with either party.

“If I get elected, and neither party is in the majority, then what I’m going to do is sit down with both sides, propose a pro-problem solving agenda, and ask both sides whether or not they’re willing to support that agenda,” he told Roll Call.

Orman also said he can’t see himself voting for either Democrat Harry Reid or Republican Mitch McConnell for Senate majority leader:

“What I’ve said consistently is both Mitch McConnell and Harry Reid have been far too partisan far too long to enjoy my support for majority leader. I think both parties would be well served by looking at someone who’s worked in a bipartisan way.”

Orman has spoken with Maine’s independent senator, Angus King, about the possibility of not caucusing with either party and essentially forming a mini-caucus of independents to force compromise in the Senate. King has caucused with the Democrats since being elected in 2012 but has said he is open to switching sides.

King “said very specifically that he would be excited about a time when he and I were in a position where neither party has a majority, that ultimately he thinks that’s one of the ways to break the gridlock in Washington,” Orman told Roll Call.

Republicans must pick up six seats in November to win a Senate majority. If they fall short by one or two, as I wrote in September, King and Orman could become independent kingmakers with the power to determine which party controls the Senate.

But the two also could abstain from caucusing with either party and possibly have even more clout.

In a recent debate with Orman, Roberts called the idea of being an independent in the Senate and focusing on good ideas rather than being attached to a party “ridiculous.” But Roberts’s response is a perfect illustration of why establishment politicians of both parties just don’t get it. To many voters, focusing on issues and getting something done instead of party loyalty doesn’t seem ridiculous.

The incredible public dissatisfaction with both political parties has been building for some time. Four years ago, I traveled the country talking to voters in Colorado, Ohio, Virginia, and New Hampshire for my book The Swing Vote: The Untapped Power of Independents. I heard how fed up people were with the dysfunction and polarization in Washington and how eager they were to try something different.

Polls bear this out. The percentage of people identifying as independents exceeds 40 percent. There are more independents than either Republicans or Democrats, and it’s the fastest growing group of voters. More than 50 percent of millennials self-identify as independents.

A recent Gallup poll revealed that 58 percent of Americans and 71 percent of independents believe this country needs a third party because Republicans and Democrats “do such a poor job.”

Orman has tapped into that feeling but done so in a fairly traditional way, by raising more than $600,000 in the first half of this year, which allowed him to run television ads this summer and increase his name recognition with Kansas voters.

Even though he is being far outspent by conservative, pro-GOP groups including the Koch brothers-backed Freedom Partners Action Fund, the National Rifle Association, and the National Republican Senatorial Committee, he’s not exactly a Mr. Smith candidate.

According to Politico, a super PAC called the Committee to Elect an Independent Senate, supported by multimillionaires Peter Ackerman and John Burbank, who also supported King’s 2012 election by spending more than $1 million, have pledged to try to elect Orman. The PAC’s new television ads call him a “bold, independent problem-solver” and “not a career politician,” and label Roberts “part of the Washington partisan mess.”

The creator of the super PAC is wealthy tech entrepreneur Thomas Layton, a friend of Orman’s.

Former New York mayor Michael Bloomberg, who also supported King and has pledged to spend $25 million this year supporting Republican and Democratic centrist candidates around the country, reportedly hasn’t made a decision yet about whether to support Orman’s campaign.

In South Dakota, another independent Senate candidate with significantly fewer resources has put a seat in play in what was previously thought to have been a safe Republican state. Larry Pressler, who served for three terms as a Republican in the Senate before losing to Democrat Tim Johnson in 1996, is running as an independent because he says the Republican Party has become too extreme and he wants to focus on problem solving.

A recent Survey USA poll showed Pressler at 32 percent, just behind Republican and former South Dakota governor Mike Rounds at 35 percent and ahead of Democrat Rick Weiland, who polled at 28 percent.

The poll also showed that if the Democrat dropped out of the race, 71 percent of his supporters would vote for Pressler, and in a head-to-head race without Weiland, Pressler would beat Rounds by 15 points.

With the race suddenly competitive, both the Republican and Democratic Senatorial Campaign Committees are planning to spend $1 million in South Dakota.

A number of super PACS also plan to buy television time in the state, including MAYDAY.US, co-founded by Harvard University law professor Lawrence Lessig, who has pledged $1 million to support Weiland.

Appearing on MSNBC on Sunday, Pressler said he hasn’t decided who he would caucus with if he won, adding it “may be the start of something big in American politics” if both he and Orman win election as independents.

The South Dakota candidate said he has directly raised about $100,000 for the campaign and is willing to put in about the same amount of his own money.

Pressler, who served in Congress for a total of 22 years in both the House and Senate, can hardly be called an outsider. But he said he has learned from his time there and is a born-again reformer.

He admits that as a member of Congress he was “part of the problem” but says he has come to the conclusion that the influence of big money and special interests on politics “is fatal to our system.” The Republican and Democratic parties, he says, have become simply “conduits of special interest money.”

A pro-choice social moderate who thinks gay marriage should be legal, Pressler says he has a mixture of Republican and Democratic views and is running to “end some of the poisonous infighting” in Congress.

Several other independent candidates are making headway this year, although they haven’t received the same kind of attention as Orman and Pressler.

In the Nebraska Senate race where polls show Republican Ben Sasse with a commanding lead over Democrat David Domina the Lincoln Journal Star on Sunday endorsed independent candidate Jim Jenkins.

Throughout the race, the businessman, rancher, and former Democrat has vowed not to caucus with either party if he won. Vastly outspent by Sasse, Jenkins is the underdog, but the Journal Star in its endorsement said electing him would be “the answer to what ails Congress.”

Jenkins is a centrist who has focused his campaign on changing Washington, reducing the debt, fixing the Affordable Care Act, and passing tax reform that closes loopholes and reduces rates.

“If Nebraskans want more of the same from Washington, they can vote for a party favorite. If they want to fix Washington, they should mark their ballot for Jim Jenkins,” the Journal Star said in its endorsement.

Orman, Pressler, and Jenkins are all very different candidates, and all three races are different as well, but what their campaigns have in common is a message stressing changing the system that is resonating with voters sick of both parties.

The same kind of campaign is being waged in northeastern Pennsylvania’s 10th Congressional District by independent Nick Troiano, a 25-year-old first-time candidate and former Republican who is running a low-budget campaign against Republican incumbent Tom Marino.

Troiano also says he thinks the GOP has become too extreme on social issues. He’s a fiscal conservative who was a co-founder of The Can Kicks Back, a millennial group affiliated with the Simpson-Bowles Commission on Fiscal Responsibility and Reform. Troiano says he decided to run for Congress after the government shutdown last year.

In this solidly Republican district, Troiano is making the argument that he is more electable than the Democrat in the race because his polling shows people are willing to vote for an independent and are not very excited about voting for the incumbent.

“Imagine the U.S. Senate with a handful of sensible independents to tip the balance in favor of workable solutions,” wrote the Journal Star in its Jenkins endorsement. “It’s not as unthinkable as it might seem.”

It’s no longer unthinkable for national political reporters and commentators, either. While in the past they’ve dismissed independent candidates and voters as not very relevant, now they seem to have had an epiphany, with a few independents not only looking like they can win but also having the potential for outsize influence in the Senate.