Democratic voters have split along generational lines in the past two presidential primary cycles. And the very early front-runner for 2020, former vice president Joe Biden has been criticized for being, well, old.

In the limited polling we have, Biden, 76, leads the pack of potential 2020 Democratic nominees, a substantial portion of whom are older than 65. On Monday, the Wall Street Journal released a survey of Iowa Democratic Party chairs that found many were hesitant to support an older candidate in 2020. The biggest worry among that group was that older candidates would not garner enthusiasm from younger voters.

“I can’t see how my generation, 18- to 34-year-olds, can get excited about a 70-year-old candidate ever again,” Bryce Smith, 26, the Dallas County chairman, told the Journal.

Beyond party officials, does early polling show that Biden has a problem with younger Democratic voters?

In 2008 primaries and caucuses where exit polls were conducted, Democratic voters younger than 30 supported eventual nominee Barack Obama by a 20-point margin (58 percent to 38 percent), while voters 65 and older favored Hillary Clinton by a similarly wide 24 points (58 percent to 34 percent). The generation gap grew to a chasm in 2016, with Sen. Bernie Sanders (Vt.) winning Democrats younger than 30 by a whopping 43-point margin, while Clinton won seniors by 42 points. Younger voters did not get their way that year.

Early 2020 polls cast doubt on the idea that Biden is destined to fare poorly among younger Democrats. A Washington Post-Schar School poll of battleground congressional-district voters in the 2018 midterms found that younger and older Democrats were about equally supportive of Biden as the party’s 2020 nominee. Among voters who supported Democratic House candidates, 35 percent of those ages 18 to 34 said they would like Biden to win the party’s 2020 presidential nomination, identical to his 35 percent support among Democrats age 65 and older.

As in 2016, Sanders in this poll received far more support from younger Democrats than seniors (31 percent vs. 5 percent), although he did not quite match Biden’s level of support, even among the youngest cohort of voters. Sanders’s strength with younger adults appears to have come more at the expense of potential candidates Michael R. Bloomberg and Sen. Cory Booker (D-N.J.) than from Biden.

An earlier CNN poll in October found Biden weaker among younger Democratic and leaning-Democratic independents when asked whom they support for the 2020 nomination. Biden garnered 33 percent support among Democratic-leaning adults overall, but his support was 13 points higher among those ages 45 and older (39 percent) than among Democrats younger than 45. Nonetheless, that age gap is smaller than it was for Clinton in 2016, and Biden’s level of support among voters under 45 is at least slightly higher than Sanders at 21 percent, Sen. Kamala D. Harris (Calif.) at 13 percent, Sen. Elizabeth Warren (Mass.) at 11 percent and others in the single digits.

A separate CNN poll in March found large majorities of younger and older Democrats at least open to supporting Biden for the party’s nomination in 2020. Among Democratic-leaning adults, 81 percent of those younger than 45 said they would be very or somewhat likely to support Biden if he runs for the Democratic nomination, similar to 86 percent of those 45 and older. Both figures were similar to or higher than those for other potential candidates tested, including Sanders.

None of the polls above guarantee that Biden will fare well among younger Democrats in caucuses and primaries, which are more than one year away. The past two cycles suggest younger and older Democrats are attracted to different types of candidates, making it one of the key factors to watch in 2020, along with racial and ideological divisions within the party.

Biden’s potential candidacy could also falter if he doesn’t generate excitement among Democratic Party officials and activists such as those highlighted by the Wall Street Journal, which could sap his campaign of donations and volunteers. But the consistency of support for Biden across age groups shows that the extremely early front-runner has appeal across generations.

Scott Clement contributed to this report.