This could be a problem.
According to Diversity Explosion: How New Racial Demographics are Remaking America author William Frey, it means the campaigns could become even more polarizing than those in recent memory.
He argued in a recent blog post for Brookings that the demographic mismatch between Clinton and Rubio and their parties' respective bases would mean "identity politics could put both candidates on the defensive — more concerned with alienating their long-held political supporters than expanding their bases to include more people like themselves."
What it means when you don't match your base
Clinton is a white baby boomer whose party's emerging base is made up of young people and people of color. Rubio is Cuban-American member of Generation X who would need to rally a group of Republican voters dominated by older white Americans.
Here's how Frey predicts that will play out:
Clinton will do her best to appeal to the Democrats' emerging base: racial minorities, young people, and selected white population groups—such as single college-graduate women—who are least inclined to vote Republican. She must promise to support the kinds of domestic programs such as the Affordable Care Act and early childhood education that are crucial to that base. Rubio cannot afford to alienate white baby boomers and seniors, now central to a Republican win, and will be cautious about how he discusses immigration reform, making sure to place emphasis on securing the borders.
That would be a big shift, he wrote, from the last two elections, when the candidates' own demographic profiles (President Obama versus John McCain in 2008 and Mitt Romney in 2012) lined up better with those of their parties' bases.
"There's just something about the identity of the candidate," he said.
"I may be wrong. I hope I'm wrong — I hope the debate over 2016 will come closer to the center and show where there's common ground," he told Vox. But he said his gut feeling is that these hypothetical campaigns could be more polarizing than ever, as the candidates compensate for their own race and age profiles by going way out of their way to please their bases.
The culture generation gap
Frey says that beneath the dilemma that could be faced by Clinton and Rubio as they try to maintain the loyalty of base voters lies a bigger problem. He calls it the "culture generation gap."
That gap, he wrote at Brookings, explains why in 2012, Obama received eight of every 10 minority votes cast while Romney received nine of every 10 of his votes from whites. Racial minorities are more heavily represented among youth, so Obama dominated voters under age 45, while Romney led among mostly white baby boomers and seniors.
"When you look at the chart you can easily see the huge divide in this country — that's the way the country's going," Frey said. "The cultural generation gap is not just politics, it has to do with social distance between the older and younger generations."
He wrote, "In essence, older white Americans do not see younger Americans as 'their' children and grandchildren and have lost a common connection."
As mostly white baby boomers leave the labor force, Frey says the onus is especially on the older generation to understand that "we need to have new productive young people moving in." That, he said, "takes investment in the next generation — investment in education, social services, bridging the gap — these young people need a lot of help. Some of them attend under-resourced segregated school systems, for example."
This type of cross-generational (and often, cross-cultural) understanding isn't out of reach, according to Frey. But if we're going to get there, it will take leadership from the very same politicians who have to navigate the culture gap just to get into office.