The fight for the future of Colorado is about education, health care and infrastructure. But it’s also about demographics. Residents are younger, more ethnically varied and less likely to be registered with either main party than those of the past. Latinos alone have grown from 9 percent of the state in 1980 to at least 22 percent today.

Candidates are jockeying to replace Gov. John Hickenlooper, a moderate Democrat, and the race is expected to be tight: The state has one million registered Democrats, one million registered Republicans and 1.2 million unaffiliated voters.

In the streets of Denver, activists have launched an effort to strip the Stapleton neighborhood of its current name, arguing that it throws salt in racial wounds, while students at Stapleton Middle School have been debating Benjamin Stapleton’s legacy, studying his biography and calling on administrators to rename their school — taking to television and radio to discuss their demands.

Mr. Stapleton, the candidate for governor, once embraced his great-grandfather, making Benjamin’s Stapleton’s civic work a top reason to elect him treasurer.

“My great-grandfather served five terms as Denver’s mayor in the 1920s, in the 1930s, in the 1940s,” he said in a 2009 campaign ad, ticking off the elder Stapleton’s accomplishments — building the airport, reinvigorating the park system. “I’m really proud of my family’s public service.”

But as residents have become more aware of his family’s ties to the Klan, Mr. Stapleton has had to tread more carefully, mostly dropping mentions of his great-grandfather from his campaign.