Secret anti-Trump donor revealed
© Greg Nash

A single billionaire provided the lion's share of the money to the main Republican super-PAC set up to destroy Donald TrumpDonald John TrumpLieu: There will be 'widespread civil unrest' if Trump fires Mueller Attorneys for Trump, Mueller hold face-to-face meeting to discuss potential interview topics: report Trump tariffs not helpful for nuclear talks, South Korea says MORE.

Marlene Ricketts, the matriarch of the Ricketts family that owns the Chicago Cubs baseball team, contributed $3 million to the anti-Trump super-PAC "Our Principles PAC," which is being run by former Mitt Romney adviser Katie Packer. 

The super-PAC has spent more than $4 million running attack ads against the GOP front-runner in Iowa, New Hampshire, and South Carolina. It is the only serious anti-Trump group to date in a campaign cycle in which Republicans have been reluctant to take on their front-runner.

Until now, the identities of the donors funding Our Principles PAC had been kept secret, fueling the rumor mill in Washington. But the Federal Election Commission reveals that almost all the money came from Ricketts. The donor's identity was first reported by The New York Times.

Ricketts's family had previously given $5 million to a super-PAC supporting the failed presidential bid of Scott Walker. The family is yet to swing its full weight behind another presidential candidate but clearly likes both Ted CruzRafael (Ted) Edward CruzOvernight Tech: Facebook faces crisis over Cambridge Analytica data | Lawmakers demand answers | What to watch for next | Day one of AT&T's merger trial | Self-driving Uber car kills pedestrian The case for a new branch of the military: United States Space Force The problem with hindsight MORE and Marco RubioMarco Antonio RubioRubio: McCabe 'should've been allowed to finish through the weekend' For Tillerson, bucking Trump became a job-killer At least six dead after pedestrian bridge collapses on cars in Florida MORE. In June last year, Marlene Ricketts gave $10,000 to super-PACs supporting Rubio and Cruz.

Besides a token $250 donation, the only other donor to the anti-Trump super-PAC in January was Illinois businessman Richard Uihlein, who gave just $7,500. 

Uihlein had previously given $2.5 million to Walker's super-PAC, but after the Wisconsin governor quit the race he shifted to the Cruz camp and recently gave $1 million to a pro-Cruz super-PAC.