LOS ANGELES Joe Biden s presidential campaign pledged to disclose his list of high-dollar bundlers but declined to give a specific timeline ahead of Thursdays Democratic presidential debate, the sixth and final of 2019.

Asked by HuffPost if he will do so before the Iowa caucuses in early February, a senior Biden campaign official said it expected the release to be forthcoming but declined to give details.

I cant commit to a date right this second, but he will be releasing his bundlers, the official said during a pre-debate briefing with reporters in Los Angeles.

Last week, South Bend, Indiana, Mayor Pete Buttigiegs presidential campaign released his list of deep-pocketed donors known as bundlers who have contributed to the campaign typically wealthy supporters of a presidential candidate who not only donate their own cash but also collect donations from others.

Of the four Democratic candidates leading in the polls, only Buttigieg and Biden have collected donations at private, high-dollar fundraisers. Sens. Elizabeth Warren (D-Mass.) and Bernie Sanders (I-Vt.) dont have bundlers, a distinction Warren pointedly attacked Buttigieg for earlier this month.

Every Democratic presidential nominee in the four most recent elections disclosed their bundlers, meaning this years crop of candidates has taken a step backward on campaign finance transparency.