good news, I wrote a 2019 post surveying two academic studies on how Buttigieg's argument was incorrect (plus more firsthand testimony from lifers). Campaign contributions from lobbyists, like Buttigieg's bundlers, leads to later legislative access and preferential policy outcomes. Free to read:
Bundlers, Lobbyists, and Access: What Studies Show About Big-Money InfluenceRecent academic studies have found that large contributions do work to ensure access for corporate lobbyists and that fundraising influences key committee assignments.readsludge.com