Former Vice President Joe Biden racked up nine victories on Super Tuesday with two contests left to call, dominating large swaths of the South and even notching a surprising victory in Massachusetts. How did he do it? According to early numbers, he can thank two key demographics: black and suburban white voters.

Turnout was up in most Super Tuesday states compared to the 2016 Democratic primary. But the bump didn’t come from the youth revolution that Sen. Bernie Sanders promised. Instead, a Washington Post analysis suggested that Biden won nearly 60 percent of voters who sat out the 2016 primary, while possibly retaining nearly 90 percent of Hillary Clinton’s 2016 primary voters.

After a sputtering start in Iowa and New Hampshire, Biden’s campaign saw a resurgence in South Carolina, driven mainly by support from older black voters. That support continued into Super Tuesday, as explained by Vox’s Li Zhou and Cameron Peters:

Biden’s victories in this trio of states were driven heavily by his success with black voters, who make up 27 percent of the Democratic electorate in both Virginia and North Carolina, and 44 percent in Alabama. These outcomes underscore just how much Biden continues to resonate with black voters, highlighting a possible challenge for Sanders — one he dealt with in 2016 as well — as the primary continues. Much like in South Carolina, Sanders appeared to do better with younger black voters in the states compared to older voters. While he still lost among black voters ages 30 to 44 in Virginia, for example, he lagged by 11 points among the group. Among black voters 45 to 59 in the state, meanwhile, he lagged by 50 points. ... The trend they show, however, could well spell trouble for Sanders. While Sanders has been polling strongly with African American voters nationally, he lost black voters by a huge margin in South Carolina, where he won 17 percent support and Biden came away with 61 percent.

Support from black voters translated across the South, with Biden notching double-digit victories in Alabama, Tennessee, North Carolina, Virginia, Arkansas, and Oklahoma. According to Washington Post exit polling data, Biden carried voters who care most about race relations, with a median 48 percent support across Super Tuesday states.

Black support explains some of Biden’s success Tuesday, but surprise victories in Texas and Massachusetts suggested there’s something else going on with Biden’s voting coalition.

In the 2018 midterms, Democrats swept into power in the House on the strength of overwhelming support not just from black voters, but from suburban white women voters as well. Exit polling from Tuesday suggests that Biden’s base tracks closely with the 2018 blue wave.

In Texas, Biden carried the Dallas and Houston suburbs. He also carried nearly every county in Virginia, including northern Virginia and the Washington, DC, suburbs. That pattern was repeated throughout much of the Super Tuesday states.

It appears, at least for now, that Biden is reassembling the coalition that fueled former President Barack Obama to two general election victories, and that faltered in 2016.