Leaders can unite or divide, whether it be by design or by misstep.

Thanksgiving’s evolution shows how both can happen.

On Oct. 3, 1863, amid profound division and upheaval of the Civil War, President Abraham Lincoln issued a formal proclamation that established a National Day of Thanksgiving.

He invited his “fellow citizens in every part of the United States…to set apart and observe the last Thursday of November as a Day of Thanksgiving and Praise to our beneficent Father who dwelleth in the heavens.”

Perfectly timed after the Gettysburg victory, the proclamation capitalized on the Union’s improved outlook and Lincoln’s emerging stature as a unifier.

Lincoln hoped a shared day of thanks would help “heal the wounds of the nation” and establish a tradition that would bond Americans for generations.

Sarah Josepha Hale hoped so too.

Editor of the magazine Godey’s Lady’s Book and author of the children’s poem “Mary Had a Little Lamb,” Hale had lobbied state and federal officials for nearly 40 years to make Thanksgiving a national holiday.

She wrote to Lincoln in the summer of 1863 asserting that only the president had the power to make the holiday “permanently, an American custom and institution.”

Presidents thereafter followed Lincoln’s example.

However, in 1939, during the Great Depression, Franklin Roosevelt issued his own proclamation. He called for Thanksgiving to be moved back to the third Thursday of November.

At the time, retailers waited until after Thanksgiving to display Christmas decorations and hold sales. By adding an additional seven days to the shopping season, Roosevelt hoped to boost consumer spending.

A Gallup opinion poll showed 62% of Americans disapproved. Roughly 80% of Republicans disapproved, while a majority of Democrats supported it.

Twenty-two mostly Democratic-leaning states observed Thanksgiving on the new date. Twenty-two mostly Republican-leaning states resisted. Three celebrated Thanksgiving on both dates.

A day meant to unite the country turned into a symbol of political difference. A reminder that partisan polarization is nothing new in U.S. politics.

Kansas Republican Gov. Payne Ratner announced that in the Sunflower State “we do not destroy tradition merely to gain newspaper headlines.”

Alf Landon, FDR’s rival in the 1936 election, criticized Roosevelt’s “impulsiveness” and strongly objected to “springing it [the change] upon an unprepared country with the omnipotence of a Hitler.”

People started calling Thanksgiving “Franksgiving”.

Amid unprecedented crises, Lincoln and Roosevelt used Thanksgiving for different purposes. Lincoln envisioned it as a path toward national reconciliation. Roosevelt saw it as a lever for economic activity.

One president embraced tradition. The other disrupted it.

Eventually, Congress intervened and established Thanksgiving as a federal holiday, restoring its observance to the fourth Thursday in November.

But here’s the irony.

Roosevelt’s vision stuck.

The partisan fight faded. Black Friday emerged as a defining feature of American consumer culture, a phenomenon widely embraced by Democrats and Republicans.

Retailers now start promotions in late October and continue through Cyber Monday.

Thanksgiving ultimately became two traditions. First a day for gratitude, then a day for deals.

Lincoln meets Roosevelt.

Oh, yes, and then there’s football.

— Mark Joslyn is a professor of political science at the University of Kansas.