After the Republicans and Democrats finished their conventions in late July, the Green Party gathered this month to nominate Dr. Jill Stein for the presidency. Stein’s campaign—with her party on ballot lines in the majority of states, and her poll numbers surging ahead of Green numbers from recent presidential elections—has the potential to be a breakthrough bid for the Greens, and for a more robust democracy.

Stein recognized the prospect in an optimistic yet urgent acceptance speech in which she spoke of “unstoppable momentum for transformational change.” The candidate who talks of ushering in a “Green New Deal” told the Green Party Convention that the party has “an historic opportunity, an historic responsibility to be the agents of that change. As Martin Luther King said, ‘the arc of the moral universe is long, but it bends towards justice.’ I know that arc is bending in us, and through us. And we are actors in something much bigger than us as we struggle for justice, for peace, for community, for healing.”

Stein’s appeal drew an enthusiastic response from her supporters, and she gained a good deal of media attention.

But there are no guarantees that her candidacy will succeed—along with that of Libertarian Gary Johnson—in clearing the way for the more diverse and competitive multi-party politics that is common in other countries but relatively rare in the recent history of the United States.

For that to happen, supporters of the Green nominee, as well as progressives who will be inclined to back Democrat Hillary Clinton in order to block the candidacy of Republican Donald Trump but who still want a broader debate, will have to advocate for something that is rare in presidential politics: fair play.

Stein is not just up against the Democratic and Republican nominees. She is up against a rigid two-party system that erects high barriers to those who seek to open up the process.

It is uncommon for independent and third-party candidates to get over and around those barriers.

But this is an uncommon year in American politics. Libertarian presidential candidate Gary Johnson is already getting close to the political high ground where a third-party candidate is treated as seriously as the nominee of one of the two major parties. And Stein is climbing as well, having just appeared on CNN for a prime-time special highlighting her candidacy. Stein’s progress is significant because, in order to have a real debate in American politics, it is vital to include voices from across the political spectrum.

A debate featuring Democrat Hillary Clinton, Republican Donald Trump, and Johnson would represent an improvement on what we have seen in recent presidential races.

A debate between Clinton, Trump, Johnson, and Stein would represent an even greater improvement.

Could it happen?

The Green nominee’s approach, and the year in which she is running, make it possible to imagine that she could find a place on this fall’s debate stages.

Stein is making her second bid for the presidency, which is an asset. Third-party candidates have historically benefited from making multiple bids. A century ago, Eugene Victor Debs made five runs for the presidency on the Socialist Party line, while Norman Thomas made six. History records that neither man won the nation’s top job. But their high-profile campaigns popularized “radical” ideas such as Social Security programs for the elderly and extending civil rights to all Americans.

Stein is mounting her bid in a moment of great political volatility, which is significant. Third parties often record strong showings in turbulent times. Debs won almost one million votes in 1920, when he ran from the jail cell to which he had been confined during the “Red Scare” assault on civil liberties following World War I. Thomas received almost as many votes in 1932, in the first presidential election of the Great Depression era.

No one knows what vote Stein may get this time, though polls suggest that both she and Johnson are running far better this year than in 2012. (The Libertarian won 1,275,951 votes that year, while the Green received 469,628.) A number of polls have Johnson, the former Republican governor of New Mexico, in double digits; and Stein has frequently been at 5 percent in recent national surveys. (In states such as California and Colorado, her numbers have been even higher.)

Does this mean that Johnson or Stein could “take off” and be elected president? History is not generous in this regard; the last time a third-party candidate surpassed either major-party contender was in 1912, when former Republican President Theodore Roosevelt (running as a “Bull Moose” Progressive) finished ahead of Republican President William Howard Taft. Both men lost that year to Democrat Woodrow Wilson, and “major” parties have dominated the top two spots ever since.

This year, both Johnson and Stein will face objections from those who fear that support for alternative candidacies might “spoil” the election by drawing votes away from major-party contenders. There is nothing wrong with this discussion; it is entirely reasonable, for instance, for progressives who are frightened by Trump’s candidacy to urge voters to support Clinton as the strongest alternative to an extremist Republican. There can and should be serious discourse about how to approach the 2016 election. But that does not mean that electoral options should be limited. The United States needs a broader politics, and the prospect that Johnson and Stein could open up the process this year ought to excite small-“d” democrats.

Even people who do not intend to vote Green or Libertarian can and should support efforts by credible contenders to secure ballot positions in states that have historically made it hard for third-party contenders to compete. It is simply wrong that the United States does not have universal election rules, creating a circumstance where obtaining ballot status is easy in some states and daunting in others.

As important as ballot access is debate access.

The Commission on Presidential Debates, which was set up by leaders of the two major parties with an eye toward controlling and constraining the most important exchanges during presidential elections, will not make things easy. Johnson is closer to the threshold that the CPD has established for debate participation—a steady 15 percent in the polls—and he is already getting the lion’s share of attention as debates about the debates ramp up.

A functional democracy should be able to find room for a real debate involving a Democrat, a Republican, a Libertarian, and a Green. As Stein’s campaign argues, correctly, “Voters have a right to hear directly from their possible choices for the highest office in the land.”

Unfortunately, that may not happen. It is quite possible—arguably likely—that both Stein and Johnson could be ruled out of the debates under the arbitrary rules established by the CPD.

That would be a travesty. And it does not have to happen.

As Reason magazine’s Matt Welch suggests, the commission should tweak its rules “if for no other reason than to fulfill its stated mission, which reads in part ‘to ensure that debates, as a permanent part of every general election, provide the best possible information to viewers and listeners.’”

“You cannot provide the best possible information by limiting the debate to Trump and Clinton—the two most disliked presidential nominees in modern history,” argues Welch. “Besides, even with our seemingly inevitable two-party sorting process, a full 20 percent of registered voters consistently indicate that they will not be pulling the lever for either D or R. Johnson and Stein, meanwhile, have combined for the same national polling percentage—just a tick below 13—both before and after the major-party conventions, suggesting that the traditional halving of third-party polls between summer and election day might not be happening this campaign season.”

The CPD can and will set baseline standards for debate participation. But those standards should err on the side of more debate, not less. The good basic approach would be to include candidates who have qualified for enough state ballots to win 270 electoral votes—the threshold for winning the presidency. Getting on that many ballot lines requires seriousness and a measurable level of support nationally, and those candidates who achieve that should be included, at the very least, in the first debate.

If the CPD insists on a more rigid standard (as is likely), then a 5 percent polling threshold—far higher than was required to gain a place on the main stage of this year’s Republican and Democratic debates—would be dramatically more reasonable than the current 15 percent threshold.

The Libertarians and the Greens will meet the ballot-line standard. And both parties can point to recent polls where they have cleared the 5 percent threshold. That should be sufficient to make room for Gary Johnson and Jill Stein on this fall’s debate stages.