WASHINGTON (AP) — Pete Buttigieg’s liberal opponents for the Democratic presidential nomination are accusing him of being beholden to big-money donors, but Buttigieg is undeterred.

He is set to attend a fundraiser on Sunday in California’s Napa Valley at an opulent winery.

The fundraiser is a measure of the unexpected success of the South Bend Mayor who has vaulted into the top tier of candidates. But it also comes with perilous optics and offers a stark contrast with his more liberal rivals.

A Buttigieg campaign spokesman says Buttigieg doesn’t solely rely on big-dollar donations and noted he has received an outpouring of small amounts, as well.