The money donated the organization, called the Our Principles PAC, was mostly from a few wealthy donors. TD Ameritrade founder and Chicago Cubs owner Joe Ricketts donated $2 million in February, reported Politico. Another $1 million came from hedge fund owner Paul Singer, plus $1 million from investor Warren Stephens.

The Republican establishment has been desperately seeking a way to beat Trump since he entered the race to high poll numbers last summer. Previous establishment favorites like Jeb Bush and Marco Rubio have all flamed out.

Despite Our Principles spending nearly $2 million of the money last month on ads attacking Trump, the New York businessman won a series of primaries in February and March and is in the drivers seat to win the Republican nomination. It is likely that the only way to defeat Trump is to deny him a majority of delegates and fight it out at a contested convention in July.