The parliamentary election in impoverished Myanmar is the most significant step yet in the Southeast Asian nation's halting journey from junta rule toward democracy, a process Clinton claims as one of her top achievements as secretary of state.
That the future of the chronically underdeveloped country, also known as Burma, is so important to the Democratic front-runner is a reminder that Clinton's record as the top U.S. diplomat in a period of intractable crises is not exactly bristling with foreign policy wins. And if events there do represent a victory, it is hardly a clear-cut one.
Clinton is in a particularly perilous position because her fate is not in her own hands: She can no longer shape events -- like the situation in Myanmar -- on which her legacy depends and on which she will be judged in the heat of a presidential campaign.
Indeed, opponents like Republican Marco Rubio are already highlighting vulnerabilities in her tenure, pointing to chaos stirred by the U.S.-led operation in Libya and a busted "reset" of relations with Russia -- both of which she championed.
In Myanmar, it is clear that the governing system produced by the political opening that Clinton and President Barack Obama pushed is far from perfect. In fact, the structure of government remains rigged in favor of the military, which ruled the country for decades with an iron fist.
Clinton's case on Myanmar
Clinton devotes an entire chapter in her memoir "Hard Choices" to Myanmar and the deep kinship she feels with another pioneering female leader, opposition icon and Nobel peace laureate Aung San Suu Kyi, head of the opposition National League for Democracy Party, called the NLD.
Clinton presents herself as the decisive driver of the U.S. effort to bring Myanmar in from the cold and toward the "tantalizing" prospect of democracy.
"I had my eyes open about the risks, but when I weighed up all the factors, I didn't see how we could pass up this opportunity," Clinton wrote, saying she was keen to prod the generals running the country to move toward political reform but wary of embracing them too fast.
The political evolution of Myanmar is so central to Clinton's legacy that she raised it at one of the most stressful moments of her presidential campaign -- a Capitol Hill hearing on Benghazi last month -- to prove her ability to bridge political divides in Washington.
"I worked with Republican Leader Sen. Mitch McConnell to open up Burma, now Myanmar, to find democratic change," Clinton said in her opening statement.
But claiming an accomplishment in the volatile country is also fraught with risk.
"Clinton needs to be careful about taking too much credit, not simply because the process was not made in America, but also because it is not complete," said Daniel Twining, a former State Department official in the last Bush administration.
Still, by any measure Myanmar has come a long way. For decades before the political thaw, it was a grim, Orwellian place, stifled by an insidious national security apparatus and isolated from the world by a paranoid military junta that used poverty and repression as instruments of power.
But the blossoming of economic and political freedoms changed life in a ramshackle nation where even Internet and mobile phones are a recent luxury. Hundreds of political dissidents were freed from hellish military prisons and Aung San Suu Kyi -- after years under house arrest -- is now a member of parliament.
While there are fears the junta will sway results or cause irregularities in voting, millions of Burmese are getting the chance to vote and the media is freer than it once was. Such an outcome would have been unthinkable eight years ago.
The United States, meanwhile, has lifted many of its sanctions on the Myanmar government and sent an ambassador back to the country. In late 2011, Clinton was the first secretary of state to visit Burma since the military clamped down in 1962.
So Clinton's claims do have some credibility.
Critics say reforms aren't enough
Critics, however, point to the military's engineering of the electoral system to weight it in its favor to counter claims that the reform process in Myanmar is as clear a triumph as Clinton might like to portray it.
"The most likely outcome of the Myanmar elections is a government that remains guided by current and former generals, despite what will be a strong showing for the NLD, and one from which Aung San Suu Kyi is excluded from executive power," according to Twining.
Though the army has withdrawn from front-line politics, and President Thein Sein has taken off his uniform, Myanmar's constitution still guarantees the military 25% of seats in parliament, whatever the result of the election. Together with the seats of the Union Solidarity and Development Party, made up of former generals, that allows the military to maintain its controlling influence on government.
Even if her NLD wins, Aung San Suu Kyi will not become president. The military, with her in mind, inserted a clause in the constitution barring anyone whose spouse or children are foreigners from serving as president. Suu Kyi's late husband and two sons are British.
Some close observers of Myanmar say the Obama administration must share the blame for the problems on the path to democracy.
"Burma is not a success story. If the administration wants Burma to be a success story, then they have got to apply greater leverage than they have on the Burmese regime to change," said Simon Billenness, executive director of the U.S. Campaign for Burma, a nongovernmental organization that campaigns for democracy and human rights in the country.
"When the Burmese regime started to open up, they did take advantage of that," he said. "But they dropped sanctions too soon and gave up their leverage."
Some critics also believe that Obama visited Myanmar -- a trip that triggered extraordinary scenes of Burmese on the streets mobbing his motorcade -- too soon.
His six-hour stay in November 2012 had the feel of a victory lap, not least because it was the last trip Clinton made with the president on Air Force One and highlighted the administration's claim that the Myanmar opening was a vindication of its Asia pivot strategy and also of Obama's signature policy of engaging U.S. enemies.
If the NLD does rack up a big win as expected -- though the primitive state of polling in Myanmar means no one is sure how Sunday's vote will turn out -- that could be seen as a vindication of Clinton's approach, despite the caveats.
Ben Rhodes, a deputy national security adviser who played an important role in the development of U.S. policy toward Myanmar, said the country is still a work in progress but said the changes in the country have validated the administration's approach.
"It is a mixed picture, Rhodes said, but added that the opening was "well, well worth (doing)" and pointed out that "the story doesn't end on November 8."
But there's also uncertainty, since in 1990 the military reacted to an overwhelming NLD election victory by simply ignoring the result, ushering in a period of crackdowns on the democracy movement and house arrest for Suu Kyi.
Meanwhile, continued violence against the persecuted Muslim Rohingya minority and multiple civil wars that have raged since the country's independence from Britain in 1948 also undermine the idea that Burma is a success story.
A country's fate in the balance
Clinton seems to have anticipated many of the problems -- and in her book, says that when she left office, Myanmar's fate still hung in the balance.
"Burma could keep moving forward, or it could slide backward," Clinton wrote.
That assessment was backed by McConnell, a frequent Clinton critic, who has worked on Myanmar policy for years and said the country still faces significant challenges.
"At the same time, we should not allow these things to completely overshadow what Burma has accomplished. It's come a long way in recent years. There are many positive things to be built upon as well," McConnell said on the Senate floor last month.
There's also the complication of just how big a share Clinton should get of whatever credit there is to claim.
"The policy of engagement that the Obama administration adopted was helpful," said Lex Rieffel, a Brookings Institution economist who has studied Myanmar and visited many times. "It did more good than harm as opposed to the sanctions policy. (But) let's not attribute the changes in that country to U.S. policy."
In her book, Clinton writes that she spotted an opportunity in early trips to Asia to work on Myanmar, especially after Indonesian President Susilo Bambang Yudhoyono told her during her first visit to Asia as secretary of state in February 2009 that the generals might be interested in a dialogue with the United States.
She also coordinated closely with Suu Kyi.
But while Clinton did play an important role in mentoring the process, the primary motive for Myanmar's opening appears to have been rooted in local and geopolitical factors.
"Burma's opening was mainly a process driven by Burmese leaders, rather than the U.S., as they sought to create strategic space against China and generate economic growth through greater exposure to the world," said Twining.
There was clearly an impulse from within the Myanmar government to shake free of self-imposed isolation. The country's poverty and lack of access to outside capital because of U.S. and European sanctions contrasted sharply with economic development in a region where states like Thailand and Indonesia were roaring ahead.
U.S. officials have privately shared stories about how the gulf between Myanmar and its fast-rising Southeast Asian neighbors was brought home at regional summits when ministers from Myanmar marveled at innovations like iPhones sported by their counterparts in other countries.
Such nuanced verdicts, like the one on Myanmar, often have a tendency to get exaggerated on the campaign trail, and any attempt by Clinton's supporters to paint her Myanmar policy as a Nixon-to-China moment would be overblown.
But if the election and its aftermath maintain Myanmar on the rocky road to eventual democracy, she would be justified in claiming a key role in an unlikely political transformation.