Stop eating junk food. Start exercising regularly. Most people have hopelessly boring 2014 New Year's resolutions. But not the nationalists of Scotland.

In just nine months' time, Scots will vote on whether to become an independent country. For Scottish nationalists, it's the culmination of a centuries-long struggle for independence. (Think Braveheart with fewer beheadings and more sober white papers on the material benefits of secession.) For unionists, the referendum risks forfeiting the many perks of London's tutelage. Beyond Scotland, the vote has wide implications for peaceful secessionist movements in multiethnic nation-states from Canada to Spain to the Balkans — putting all the more pressure on Scottish partisans to fulfill their 2014 New Year's resolution: win over undecided voters.

“This issue of the referendum is whether Scotland is better off without the United Kingdom,” David Mundell, the under secretary of Scotland, told Foreign Policy. “Obviously, we make the case that it's better as part of the United Kingdom.”

Mundell has become London's poster child for keeping the United Kingdom united, and has spent part of December carrying that message to Washington in meetings at think tanks and influential congressional offices. A lifelong Scotsman, Mundell is the only Conservative MP who represents a Scottish constituency, making him an ideal courier for David Cameron's anti-independence message.

“He's a rare bird,” said the Brookings Institution's Fiona Hill, “And perhaps more effective than having some British official who doesn't have the same cachet.”

Sitting down with FP at the British Embassy in Washington, Mundell's message was simple: Scotland doesn't realize how much it has to lose as a tiny independent state of 5 million people. “I would rather be part of a Scotland that has an influence in the world than be part of a Scotland [with] absolutely no influence,” he said.

As a part of the U.K., Scotland enjoys the benefits of London's longstanding clout in an array of international institutions from the United Nations, where it holds a seat at the Security Council, to NATO, to the European Union to the G8 and the G20. In a chaotic global economy, it also helps to belong to a country with a substantial credit line. In 2008, the British government bailed out two of Scotland's biggest banks, the Royal Bank of Scotland and HBOS. “If it hadn't been for the wide resources of the United Kingdom, Scotland would've been like Iceland where effectively the country went bankrupt,” said Mundell.

Mundell was gearing up for a talk at the Brookings Institution the next day, where his intellectual rival, First Minister of Scotland Alex Salmond, spoke earlier in the year. Both men make compelling points, but there's a sense that they're speaking past each other. While Mundell talks economies of scale and the pragmatic downsides to independence, Salmond drapes his appeal in the universalist rhetoric of self-determination.

In his April address at Brookings, Salmond summoned the memory of President John F. Kennedy. “I think there is a universal truth that people who take the best decisions about a nation's future are the people who live and work in that nation,” he told the audience after an introduction by the influential Middle East peace negotiator Martin Indyk. “No other country is going to make better decisions about Scotland than the Scots will.”

Salmond envisions a nuclear-free Scotland with an expanded social safety net and a Scandinavian-style foreign policy that emphasizes benevolent global citizenship rather than hard power realpolitik. It's clear his message has found an audience. On a secessionist platform, Salmond's nationalists won their first election in 2007 and won a majority in 2011. According to recent polling, the nationalists have an uphill battle ahead of the Sept. 18 referendum, but have swayed enough Scots to keep London worried.

In a December poll taken after the Scottish government released its white paper on a succession plan, 27 percent of those surveyed said they'd vote “yes” for independence while 41 percent planned to vote “no.” Since last September, the anti-independence movement's lead has shrunk from 19 percent to 14 percent.

“The odds are against independence, but as we know from many previous instances of polling and elections, there's always a chance for a surprise outcome due to external events,” said Hill. “The Scottish government just released the white papers on independence so they're now in full-court press mode.”

In recent days, senior Tory leaders have expressed concern that Scottish nationalists are gaining ground in the debate and have called on Cameron to reinvigorate his anti-independence campaign. Speaking to the Spectator, Cameron said he wasn't losing sight of the issue. “We cannot in any way let this argument go the wrong way,” he said. “We've got to fight every day. It's one of the biggest issues of next year, if not the biggest.”

Beyond Scotland's boundaries, the independence movement is a source of anxiety for multi-ethnic countries and a source of hope for the Catalans and the Quebecois in their own bids for nationhood.

In a shot across the bow, Spanish Prime Minister Mariano Rajoy warned in November that Scotland would be kicked out of the European Union if it voted for independence from Britain. “It is clear to me that a region which asks for independence from a state within the European Union, will be left outside the EU,” he told reporters. Given Spain's staunch opposition to independence for Catalonia, an autonomous community in Eastern Spain, Rajoy does not want to set a new precedent for breaking up sovereign states. Spain's opposition is a headache for Salmond, who has pledged that EU membership would be a priority for independent Scotland.

Meanwhile, Scottish independence has caused excitement in Quebec, where premier Pauline Marois has offered to share notes with Salmond given her experience with pro-independence bids in Canada in recent decades. Salmond, however, has avoided comparisons to other independence movements. “Scotland isn't Catalonia. We're not Denmark. We're not Ireland. We're not Quebec,” he said in April. “Scotland is Scotland.” This detachment came to a head in January when Salmond appeared to snub an effort by Marois to offer him independence guidance in a public meeting. At the time, the CBC speculated that “he may not have been eager to be seen in public with the leader of a party that had lost its own independence votes, twice, in 1980 and 1995.” Burn!

But pro-independence leaders aren't the only ones who'd like to avoid the Quebec experience. The political and economic uncertainty caused by the French-speaking province's repeated independence efforts over the last three decades concern Mundell, who wants the Scottish referendum to settle the matter regardless of the outcome. “I hope we have a decisive result that puts it to bed for at least a generation,” he said. “It actually does become very damaging in terms of creating uncertainty and instability. . . . Constitutional debate doesn't grow the economy, it doesn't help children's education or get people better medical care.”

John Hudson is a staff writer for Foreign Policy.