(CNN) The dominant assumption among Democrats for years has been that the best way to expand the Electoral College map is to expand the electorate by turning out millions of additional young people and minorities . But Joe Biden 's campaign may be pointing Democrats toward a different path to widening the presidential battlefield.

The former vice president's surprising strength among older voters in polls could offer him an unexpected opportunity to broaden the electoral map, even if he struggles to mobilize large numbers of new voters.

People older than 45 composed a larger share of voters than the national average in 2016 in all six states that both sides consider the most likely to pick the next president, especially Arizona Michigan and, above all, Florida , according to census figures. Improving on the Democratic performance among those seniors offers Biden an alternative route to tipping the six key swing states -- which also include North Carolina Pennsylvania and Wisconsin -- than by exciting more young people to vote, which could prove a difficult challenge for him.

"If there are significant shifts in support demographically then you don't necessarily need to boost turnout," says Democratic consultant Michael Halle, who directed Hillary Clinton's battleground state strategy in 2016.

Many Democratic operatives still believe that the party's long-term future will pivot on its capacity to increase turnout among younger and nonwhite voters, especially in the Sun Belt states growing in population. But that conviction is giving way to a growing awareness that the potential path to victory for Biden, given his own unique strengths and weaknesses, may rely less on that forward-leaning mobilization than on a throwback strategy of reducing Donald Trump's elevated margins from 2016 among older and blue-collar white voters to the slightly smaller advantages Republicans enjoyed with them 15 or 20 years ago.

"The idea that expanding the map comes down to high mobilization of the constituencies that give you the most support doesn't necessarily follow," says Ruy Teixeira, a longtime liberal election analyst and senior fellow at the Center for American Progress. "You can do the same things by reducing your deficits or becoming competitive among groups where you had been doing quite poorly."

Race and age intertwine politically

While some other national polls still show Trump leading with seniors and near-seniors, the general trend line with older voters is more favorable for Biden than it has been for recent Democratic nominees. At the same time, many political professionals in both parties remain uncertain that Biden can excite a large turnout among young people , especially those of color, who rejected him in big numbers during the Democratic primary and have displayed only modest enthusiasm for him in most early general election polls.

"He is not the spark to that flame, for sure," says Republican strategist David Kochel.

Those trends among the young still concern many Democratic operatives. But a closer look at the demographics of the swing states makes clear that for Biden a strategy centered on appealing to older voters, most of them white, could substitute for mobilizing young people, many of them diverse, in all of the places that both sides consider pivotal in 2020.

"It was never clear to me that the way you expand the map was by enormous turnout among young people," said Teixeira. "Other moving parts were just as important, if not more important."

In all six of the Rust Belt and Sun Belt swing states, people older than 45 cast a higher share of the 2016 vote than they did nationally, according to calculations from census figures by William Frey, a Brookings Institution demographer. In Pennsylvania (62%), Wisconsin and North Carolina (63% each), those older voters constituted a slightly larger share of the total than the national number (61.8%); the gap was greater in Arizona (64%), Michigan (65%) and above all Florida (67%).

Across all six of these pivotal battleground states, age and race intertwine politically. In each of them, the younger generations are more racially diverse than the older. That pattern is especially pronounced in the Sun Belt states. In the 2016 presidential election, exit polls showed that in Arizona nonwhites constituted 44% of the voters younger than 30 but only 12% of the seniors who voted, according to calculations by CNN polling director Jennifer Agiesta; in Florida, the numbers were 56% among the young and just 21% among the seniors.

In the Rust Belt states, the minority share of the youth vote isn't as great, but even in those places the "racial generation gap," as Frey has called it, is formidable: Minorities constituted nearly two-fifths of the younger voters in Michigan last time, but only 1 in 7 of the seniors. In Pennsylvania and Wisconsin, whites made up more than 8 in 10 2016 voters aged 45-64 and more than 9 in 10 of those older than 65, Agiesta found.

Because of that demographic makeup, the Rust Belt has always been an uneasy fit for the strategy that many liberals prefer of mobilizing more younger minority nonvoters. Not only do whites represent a larger share of actual voters in the Rust Belt than in the Sun Belt, but they also compose a clear majority of the adults who were eligible to vote but did not in 2018. (At least three-fourths of eligible nonvoters in 2016 were white in all three big Rust Belt battlegrounds, according to calculations by David Wasserman of The Cook Political Report.)

In those states, there's a general acknowledgment among Democrats that the party has no choice but to improve its performance among white voters, particularly the older whites who strongly preferred Trump last time: In Pennsylvania, Michigan and Wisconsin alike, the exit polls found that Trump routed Hillary Clinton by almost identical margins of about 2 to 1 among whites who were older than 45 and lacked college degrees, according to the results provided by Agiesta.

2018 field tests

Mobilization of nonvoters is potentially a viable strategy for Democrats in Sun Belt states that are adding population and rapidly growing more racially diverse, particularly among their younger generations. In those states, there are large pools of younger nonvoters available for the party to activate -- if it can inspire them to the polls.

But even there, a stronger performance among seniors could offer Biden an alternative path to victory, especially in the states that both parties are most targeting in 2020: North Carolina, Florida and Arizona. In each of those three big battlegrounds, Frey found that in 2016 voters older than 45 turned out at much higher rates than younger ones, just as they did in the three critical Rust Belt states.

"If you can trim off a little bit of the folks who you know absolutely will vote, that is far more effective than trying to turn out folks who have a very low propensity of voting," says Mike Noble, a former Republican consultant in Arizona who now polls for nonpartisan clients.

To some extent, these alternative approaches for Democrats were already field-tested across the Sun Belt in the 2018 elections.

Inspiring more turnout among those younger, mostly nonwhite, voters in diversifying states was the strategic underpinning for three of the 2018 campaigns that most electrified Democrats nationwide: the governor campaigns of Andrew Gillum and Stacey Abrams in Florida and Georgia, respectively, and the Senate campaign of Beto O'Rourke in Texas.

Offering a passionate case for fundamental change, each generated commanding margins among younger people: All three carried almost exactly three-fifths of voters aged 18-44, according to figures provided by Edison Research, which conducts the exit polls for a media consortium that includes CNN.

All three inspired large turnout and enormous enthusiasm from volunteers and donors alike. But each of them nonetheless lost their races because they faltered with older voters. Abrams and O'Rourke each carried only a little more than 2 in 5 voters older than 45, and Gillum did just slightly better, posting 45%, according to the Edison Research results. Among whites older than 45 the results were even grimmer: Gillum carried slightly fewer than 2 in 5 while O'Rourke won fewer than 1 in 3 and Abrams only a little more than 1 in 5. (O'Rourke and Gillum struggled as well with older Latinos, the exit polls found.)

By contrast, with much less national attention, Democrat Kyrsten Sinema won a US Senate seat in Arizona that same year by moderating her earlier liberalism and running as a centrist who would build bridges across party lines. Like the other three Sun Belt Democrats, Sinema struggled among older working adults aged 50-64, according to the exit polls; but unlike them she carried a majority of seniors, which helped her squeeze out a narrow victory over Republican Martha McSally. Sinema carried 44% of whites older than 45, a measurable improvement on the other three.

One possible model for Biden

One of the most striking aspects of Sinema's win was her victory in Maricopa County, centered on Phoenix. Maricopa was the largest county in the US that Trump won in 2016, but Noble's post-election analyses found that 88 precincts that backed the President in 2016 switched to Sinema two years later. Those included many suburban areas crowded with college-educated voters who broke from Trump nationwide. But when Noble and his team analyzed the Maricopa precincts that moved away from the GOP from 2016 to 2018, he found two retirement communities at the very top of the list: Sun City and Leisure World.

Noble says he believes that those seniors first pulled back from the GOP around its efforts to repeal the Affordable Care Act in 2017. His latest statewide poll, which showed Biden leading overall, showed him besting Trump among voters older than 55.

That's catastrophic for Republicans in Arizona, he notes, since the heavy Latino presence in the younger population reliably tilts it toward the Democrats. (Sinema won three-fifths of voters younger than 45 in 2018.) If Biden can maintain an advantage with those older voters through November, Noble says, "it's smooth sailing" for him in the state, especially since Trump and the GOP are also eroding among younger college-educated suburbanites.

Clifford Young, the president of Ipsos Public Affairs, says the firm's own recent polling has found Biden running even or ahead of Trump among seniors in the big three states of Michigan, Pennsylvania and Wisconsin. After Trump's unusually strong performance among those voters in 2016, he believes, "what you are seeing is some migration back to status quo ante 2016," when Democrats ran more competitively with older Midwesterners.

Kochel says the fact that many older voters in the Midwest live in rural communities that feel a strong cultural connection to Trump -- and have also generally been less affected by the coronavirus outbreak -- will ultimately create challenges for Biden among the region's seniors. But he adds that the movement toward the Democrat among older voters "is no doubt something [Trump] has to be watching real close."

The most important thing about the movement among seniors in recent swing state surveys may be that they open a new front of vulnerability for Trump. In 2018, the GOP performed poorly in many white-collar suburbs around the country but Democrats recorded only small gains among seniors. Now Trump faces the prospect of confronting both of those challenging trends at once across the key battleground states.

"Just these suburban numbers alone put Biden in a position to win pretty handily," says Halle, who served as a senior adviser in Pete Buttigieg's campaign this year. "If you start to bleed other places -- and the senior numbers is a significant place where Trump is bleeding in the most recent round of numbers -- you just don't have enough putty to patch all the holes."