Editor's Note: This post is part of "Cybersecurity and Election Interference," a Brookings series that explores digital threats to American democracy, cybersecurity risks in elections, and ways to mitigate possible problems.

In July 2016, candidate Donald Trump famously encouraged Russia to find Hillary Clinton’s missing emails. At a press conference, he said “Russia, if you’re listening, I hope you’re able to find the 30,000 emails that are missing. I think you will probably be rewarded mightily by our press.” That same day, according to a federal indictment unsealed last year, Russians sought to hack Clinton’s personal servers and a few months later, Wikileaks released sensitive emails to the general public.

Much has been made in recent months about the likelihood Russia will steal emails and engage in disinformation during the 2020 campaign. In his congressional testimony, Mueller openly predicted Russia would do that as part of its general effort to destabilize American democracy. He urged Americans to remain vigilant about this possibility.

Yet the risk of foreign intervention goes far beyond Russia. Indeed, this type of action has happened many times in U.S. history. In 1796, for example, rivals England and France contested the presidential campaign on opposite sides of the race. Smarting from its defeat in the American Revolutionary War just a few decades earlier, England saw the Federalist John Adams as more sympathetic to its side, while France favored Thomas Jefferson, who had served as the U.S. Ambassador to the French in President George Washington’s administration and was more open to the aspirations of the French Revolution.

In 1940, Germany encouraged Charles Lindbergh’s isolationist sentiments against President Franklin Roosevelt. It saw isolationism as a way to keep America from providing material support and entering the war on the side of France and England. Later, the Nazis unsuccessfully tried to help Republican nominee Wendell Wilkie through releasing documents hostile to Roosevelt.

In 1984, the Soviet Union was not happy with U.S. President Ronald Reagan. Its leaders saw him as bellicose and militaristic, and boosting defense spending at an alarming rate. In an effort to find material that might undermine the president, it spied on the Republican National Committee, but did not find anything that stopped Reagan’s reelection.

In 1996, there were allegations of illegal Chinese campaign contributions to the Democratic National Committee. At the time, China was worried about hostile policies from the Republican party and thought President Bill Clinton was more supportive of its economic development plans. It was a crucial time in Chinese history because its government was edging towards more international trade and wanted to be sure Western nations would not block its growth.

What’s new in 2020 is that, over the past few years, Russians have shown other nations how easy it is to sow disinformation and disrupt democratic elections. Many countries, including the United States, seek to make the voting process easy so balloting is designed much more for user-friendliness than electoral security. At the same time, technology companies have created social media platforms that are easily exploited through disinformation, false news, and fake videos. What’s more, the use of this technology to disrupt campaigns is cheap and difficult to trace.

The stakes of the upcoming election extend way beyond the shores of the United States. Due to its global impact, what happens in America has tremendous implications for other countries. Our policies affect the economic development opportunities, competitiveness, and security of other places. U.S. actions increase incentives for foreign entities to seek to influence the U.S. campaign. It matters considerably to other nations who wins and what happens in terms of U.S. foreign and trade policies. The economies of other nations will rise or fall depending on who emerges as the next American president.

Recognizing this possibility, President Trump has baited China with an August 1 tweet saying “China, Iran & other foreign countries are looking at the Democrat Candidates and ‘drooling’ over the small prospect that they could be dealing with them in the not too distant future. They would be able to rip off our beloved USA like never before.”

His taunt raises the prospect of foreign campaign intervention in 2020 may extend way beyond Russia to countries such as China, Iran, North Korea, Saudi Arabia, and others that have a major stake in the electoral outcome. Foreign governments recognize there will be differences between dealing with Trump, Joe Biden, Elizabeth Warren, Bernie Sanders, Kamala Harris, Pete Buttigieg, or Cory Booker as the next American leader. Each has different values, policies, and visions that will impact foreign lands.

In an interview on Rachel Maddow’s MSNBC television show, Hillary Clinton anticipated a scenario of other governments contesting the American election. She raised the prospect China may try to undermine President Trump by saying “China, if you’re listening, why don’t you get Trump’s tax returns? I am sure our media would richly reward you.”

Imagine a 2020 campaign where Russia, Saudi Arabia, and North Korea engage in U.S. activities designed to re-elect Trump while China, Iran, and others seek to undermine him. Americans could wake up the day after the election not knowing whether they were manipulated into an election outcome by direct or indirect foreign activities. The mere possibility of that happening should unsettle all Americans.

In the lead-up to the 2020 election, many nations worry whether a second Trump term will advantage or disadvantage them. China is in the midst of a trade war launched by President Trump. Iran sees Trump as openly hostile to its interests. The Saudi kingdom has benefitted from close ties to the Trump family. North Korea Leader Kim Jong Un has forged a friendly relationship with President Trump and therefore may want to see him remain in office.

While this list could go on to include other countries, including those friendly to the United States, it is clear the 2020 stakes are high in many places around the world. With the Russian disinformation playbook on open display for all to see and use, the ease of intervention may lead to a campaign contested by many foreign agents. U.S. authorities, news organizations, and voters will need to remain vigilant about a wide range of foreign threats.