The fate of the European Union—and short-term the stability of global markets—may now reside in the hands of United Kingdom’s voters.

Investors are holding their breath as voters in Great Britain and certain parts of the Commonwealth of Nations decide whether the U.K. will remain part of the EU on Thursday.

Whether voters choose to leave, or “Brexit,” the EU or remain, there will be lasting implications that may take years to realize, says Tom Stringfellow, president and CIO of Frost Investment Advisors, a San Antonio, Texas-based asset manager.

“Although the results of the vote are yet to be realized, the ongoing debates point to fairly serious economic, regulatory, political and nationalist consequences,” Stringfellow says. “One of the more significant risks that could be unleashed is the threat of a further unraveling from the peripheral nations of the EU, such as Italy, Spain or Greece.”

Stringfellow cites analysis by the U.K. Treasury that estimates that a Brexit would lower the country’s GDP by 3.6 percent after two years and raise unemployment by 520,000, while launching a massive overhaul of regulations, contracts and laws.

Yet concerns over the long-term global market impact from a Brexit may be overstated, says Michael Arone, chief investment strategist for Boston-based State Street Global Advisors.

“In the short term, you’re likely to see some volatility in stocks and currencies, and in the fixed income market,” Arone says. “The brunt of the volatility will be felt in gilts, sterling and U.K. stocks, but that will probably last a short amount of time, as little as a couple of days or a week.”

Oddsmakers and polls indicate the "Remain" faction is in the lead, but the polling is close enough that it’s anyone’s guess what British voters will decide, says Arone.

While aftershocks from a vote to leave the EU could ripple throughout the global economy, Arone says that the impact could be a positive one for U.S. investors as gold, the dollar and U.S. Treasuries would enjoy a boost.

Simon Ward, chief economist at Chicago-based Henderson Global Investors, said the immediate impacts of the vote really depends on the market environment it occurs in.

“Global economic growth has been weak but stable in early 2016, and the view here —based on monetary trends and leading indicators — is that it will strengthen during the second half," Ward said. “[That] suggests that the negative impact of a Brexit vote on global markets would be smaller than many fear.”

Dave Haviland, a managing partner at Needham, Mass.-based Beaumont Capital Management, also believes that fears of a major Brexit-driven drawdown are overstated, as are concerns of an end to European unity. "They're not going to blow up the Chunnel. I believe something like 40 percent of the U.K.'s trade occurs with other EU memebr states. They're not going to all of the sudden have 40 percent of their goods, services and capital simply cease to transact."

Long-term consequences, on the other hand, depend more on the manner of the Brexit, says Arone.

“What will ultimately happen is that negotiations to exit the EU will likely take as little as a couple of years to upwards of seven years,” Arone says. “What’s interesting is that the ‘Leave’ campaign has been built on the idea that the U.K. would still have access to the European single market.”

In commentary drafted on Wednesday, Lyndon Man, senior portfolio manager at Atlanta-based Invesco, said that while the British could still participate in the EU economy, they would have to accept EU regulations, contribute to the EU budget and accept the free movement of people across their borders, issues that helped lead to the Leave campaign in the first place.

Also impacted would be cross-border banking, which is currently possible in Europe through EU legislation. A Brexit would undo 40 years of regulation, said Man, leading to a long and costly unraveling process.

“Even in the event of a Brexit, the U.K. will still be a EU member for at least two years to allow for a new relationship with the EU to be agreed to maintain access to the single market, and hence alleviate the risk of a ‘cliff-like’ impact,” Man said. “That being said, given that the financial service sector has a trade surplus with the EU, and London’s esteemed status as the key European financial center, it will be more sensitive to an exit.”

Haviland says EU rules requiring the free movement of peoples are the real focal-point of the Brexit debate.

European countries are experiencing an influx of immigrants from north Africa and the Middle East at a time when birth rates among indigenous populations are in decline, says Haviland. The growing presence of immigrant populations, who often have larger families, is viewed by some as a threat to their indigenous cultures.

“I think the Brexit is driven by trade much more by immigration and the movement of people rather than trade and finance per se,” Haviland says. “Right now there are a lot of issues with immigration, and the indigenous populations in Europe feel like they’re under pressure. There’s an overlay: These government systems are much closer to socialism than they are in the U.S., so people are wondering how they will pay for healthcare, pensions and education as immigration surges. The Brexit vote is nothing more than a manifestation of fear.”

Whether or not the British choose to leave the EU, the close polling and rise of nationalism and populism have become a global political theme in recent months, with the rise of the Golden Dawn movement in Greece, the rebounding popularity of Marine Le Pen’s National Front in France and the rise of Donald Trump in the U.S. to become the Republican Party’s presidential nominee.

These right-wing movements all focus on anti-immigration, pro-sovereignty and anti-trade sentiments, says Arone, and thrive during periods of rising inflation and stagnant economic growth.

“In order to turn the tide and to get a broader number of folks feeling positive about the economy, we need higher growth rates,” Arone says. “Even if the U.K. votes to remain, the rise of these epolitical parties and their ability to gain some share in government is going to have policy implications moving forward. It becomes harder to enact free-trade policies, and that oculd pose a broader challenge to economic growth in the future.”

Thus, the political debate over local sovereignty and trade could become a feedback loop—stagnant growth drives voters to far-right populist movements, whose policies obstruct free trade and drive down the economy, leading to further stagnation.

The vote comes amidst volatility that followed polling on the likelihood of a vote to leave the EU. When surveys of British voters found growing support for Brexit earlier this month, markets responded with a sharp decline, only to rebound when subsequent polls found a narrow lead for remaining in the EU.

“What’s happened now is that the financial markets are voting machines that ebb and flow on sentiment, so these polls provide information that moves them directionally,” Arone says. “Longer-term, markets still move on fundamentals and are weighing mechanisms. They’re both overreacting and underreacting in the short-term to information.”