Mostly, it’s the economy, stupid. Not really tax policy, says this study: https://theconversation.com/what-influences-american-giving-78800
Rage Fundraising
Progressive nonprofits are raising more than the Democratic Party (“more bang for the buck”): http://www.newsweek.com/why-dnc-struggling-fundraise-while-rnc-liberal-groups-thrive-641344