Fred Eshelman, the donor, is suing Houston-based "True the Vote Inc" for what he claims are "empty promises," Bloomberg reported.
True The Vote claimed it had a multi-part plan to "investigate, litigate and expose suspected illegal balloting and fraud in the 2020 general election," the lawsuit said.
The group claimed it also collected whistle blower complaints, supported GOP legislative fights in swing states and conducted "sophisticated data modeling and statistical analysis to identify potential illegal or fraudulent balloting."
In the weeks after the election, True the Vote filed four lawsuits, but dropped them all last week.
“While we stand by the voters’ testimony that was brought forth, barriers to advancing our arguments, coupled with constraints on time, made it necessary for us to pursue a different path,” the group wrote on its website on 17 Nov.
Mr Eshelman supported the group under the pretense that they would find evidence of voter fraud. However, as their lawsuits failed - as have almost all of the lawsuits filed by supporters of Mr Trump in attempts to overturn the election - Mr Eshelman has decided he wants a refund.
He claimed that he "regularly and repeatedly" asked True the Vote Inc for updates on their initiatives, but was given "vague responses, platitudes, and empty promises."
According to Mr Eshelman, True the Vote offered to give him $1m to drop his lawsuit.
True the Vote has not responded to press requests for contact.
The Trump campaign has yet to produce convincing evidence of widespread voter fraud having any notable impact on the election. Of at least 38 lawsuits filed by the Trump campaign, 26 have failed to gain traction in the courts.