Former Vice President Joe Biden has built his early polling lead in the 2020 Democratic primary on the argument that he is the Democratic candidate best positioned to take on President Donald Trump. He referenced his standing against Trump in the first TV ad he ran and has spoken repeatedly about winning over Republican voters who, he argues, have grown disenchanted with the president.

But in at least one “electability” metric, Biden is lagging behind his Democratic competition. In the 206 counties that voted for Barack Obama twice before backing Trump in 2016, the former VP has fewer donors than three primary opponents.

According to an analysis of Federal Election Commission data on the Democratic online giving portal ActBlue, 12,040 donors from those Obama-Trump counties made 19,885 donations to Biden during the first six months of 2019. By contrast, Sen. Elizabeth Warren (D-MA) had 13,674 donors make 26,298 donations from those counties and South Bend Mayor Pete Buttigieg had 14,294 donors make 23,320 donations from those counties.

Biden has only been in the race since late April, compared to Warren and Buttigieg, who had launched presidential exploratory committees by the beginning of 2019 and late January respectively. But the latter two have had stronger fundraising months more recently. All three of them trail Sen. Bernie Sanders (I-VT)—whose campaign helped compile the data—when it comes to donors from Obama-Trump counties. The Democratic-Socialist had 33,185 donors make 81,841 donations in those areas, a haul that his team was eager to tout.

"To defeat Donald Trump, we will need to drive turnout to historic levels in every county in America—and these numbers show that Bernie Sanders’ campaign is building a huge and diverse grassroots movement to do exactly that,” campaign manager Faiz Shakir told The Daily Beast, calling his candidate “best positioned to defeat Trump.”

Sanders has led the Democratic field in terms of sheer number of givers by a wide margin. The senator, according to an aide, now has more than 2.5 million contributions and more than 900,000 individual donors overall. So the fact that he is beating Biden in these specific counties is not overly shocking.

Nor is it clear whether donations will directly translate into votes. Not all primary voters give to candidates. And data on campaign giving does not include the party identification, meaning that Sanders—and, to a lesser degree, Warren and Buttigieg—may be getting a boost from over-excited progressives and not those Democrats who left the party for Trump in 2016.

Still, the data point could present potential problems for Biden, whose main hurdle in the path to the nomination seems to be a hiccup in an early primary state. Of the 206 counties that swung from Obama to Trump, Iowa played host to the highest number with 31.

Biden and his team have made the case that he can resuscitate the Obama-era Democratic coalition and have leaned heavily on public opinion polls showing him beating Trump in hypothetical matchups by larger margins than his primary opponents. Sanders campaign has responded by noting that he has consistently beat Trump in early head-to-head polling too; in fact, the senator’s team has tried to make a concerted effort to prove that he is more electable that Biden.

Biden’s campaign did not offer comment on the record.