Dracs pointed me to a new Priority Club multipartner bonus.
The offer is up to 6000 bonus points: 1000 for the first partner, 2000 for the second partner, and 3000 for the third partner activity.
Register and complete eligible activity by March 31. All activity has to post to your account by June 15, and points should post in the second half of June.
I just transferred 2 American Airlines points into 1 Priority Club point at Points.com for my first partner. I might transfer the minimum amount from American Express Membership Rewards or Diners Club and do one shopping transaction in order to hit my three partners.
The last partner bonus offer was up to 4 partners and 10,000 miles, so this one isn’t as lucrative. Priority Club had a real problem correctly distinguishing partners and posting earned points last time, see for instance here and here.