Grover Cleveland is the only president to win non-consecutive terms: NPR

If Trump wins re-election, he would be the second president in U.S. history to serve non-consecutive terms.

The first was Grover Cleveland, who served in the White House twice, from 1885 to 1889 and from 1893 to 1897.

How did that happen?

An introduction to the country's 22nd and 24th presidents

Cleveland, a lawyer, entered politics in his 40s as an anti-corruption reformer. He was elected mayor of Buffalo, NY in 1881 and governor of the state three short years later.

Cleveland was nominated as the Democratic Party's presidential candidate in 1884 overcame a sex scandal narrowly defeating his Republican opponent, Senator James Blaine of Maine. He was the first Democrat elected after the Civil War, which ended in 1865.

His first term was marked by several big moments, including fatal ones Haymarket riot of 1886 in Chicago, which became a symbol of the fight for workers' rights, and the passage of the Interstate Commerce Act in 1887, which established federal regulation of an industry (railroads) for the first time.

Cleveland, who was elected as a bachelor, also married during his presidency only president to do so in the White House.

But he also made some decisions that angered his critics, such as vetoing private pension bills for Civil War veterans and money to distribute seed crops to drought-stricken farmers.

He ran for re-election in 1888, but lost to Republican candidate Benjamin Harrison – a colonel in the Union Army during the Civil War and grandson of former President William Henry Harrison.

A portrait of Grover Cleveland, the 22nd and 24th Presidents of the USA

National Archives/Getty Images/Hulton Archive

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National Archives/Getty Images/Hulton Archive

Cleveland's re-election campaign went poorly in many ways, says presidential historian Troy Senik said History.com.

“He began the race without a campaign manager, delegated most campaign tasks to his running mate Allen Thurman, who at age 74 was not healthy enough to withstand the rigors of campaigning, and based the entire race on him.” Cutting tariffs divided his own Democratic Party and united Republicans in opposition,” Senik said.

Cleveland won the popular vote – 48.6% to 47.9% – but lost the Electoral College vote. He moved to New York City and practiced law.

So what attracted him back to the election campaign?

Barbara Perry, co-chair of the Presidential Oral History Program at the University of Virginia's Miller Center, told History.com that Cleveland had no plans to run again after his first term but was increasingly dissatisfied and fearful of his party's populist leanings , that nominating another candidate would “lead the party to the kind of cronyism he had fought so hard against.”

What's notable, she said, is that his decision to run again was made before the modern primary system – and therefore didn't engage voters in the same way it would today. He was nominated in 1892 and ran again against Harrison.

This time, with the country on the brink of an economic crisis and now more receptive to lowering tariffs, Cleveland won in a landslide.

His second term was also dominated by economic and labor issues, from the economic crisis known as the Panic of 1893 to the Pullman strokewhich crippled rail service throughout the Midwest and marked the first time the federal government used an injunction to break a strike (it also led to the establishment of Labor Day as a conciliatory gesture).

Support for Cleveland from his own party declined during his time in office. After leaving the White House, he retired to Princeton, New Jersey, where he lived until his death in 1908.

While Cleveland was the only president to succeed in winning non-consecutive terms, he was not the only one to try.

Martin Van Buren, who served from 1837 to 1841, attempted to run as a third-party candidate in 1848. Millard Fillmore, who served from 1850 to 1853, ran again in 1856. Theodore Roosevelt, who left the White House in 1909, unsuccessfully ran for a third term in 1912.

More than a century later, Cleveland is still one club — and Trump is eager to join.