The Constitution doesn't stop candidates from running for president while serving jail time.
Two previous candidates, Eugene V. Debs in 1920, and Lyndon LaRouche in 1992, both ran from prison.
If Trump is convicted, it's possible he could run for president from behind bars.
Eugene V. Debs was in an Atlanta penitentiary, serving a ten-year sentence, when he lost the 1920 presidential election. Two years earlier, Debs, a labor leader, had spoken out against America’s involvement in World War I. He was convicted of violating the Espionage Act of 1917, after the prosecution argued that his antiwar speech obstructed military enrollment. The 1920 loss didn’t come as a surprise to Debs, who had run four times before. His fifth and final run, promoted with a campaign button that read “For President Convict No. 9653,” brought him nearly one million votes, says Claire Jerry, curator of political history at the National Museum of American History . President Harding commuted his sentence in December 1921.
Source: Smithsonian Magazine