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Actor and Senate candidate Hill Harper, left, and Sen. Rashida Tlaib.
CNN  — 

Hill Harper, a Democratic candidate for a US Senate seat in Michigan, said a donor offered him $20 million in campaign support if he were to agree to end his Senate bid and instead mount a primary challenge against Rep. Rashida Tlaib.

In a post on X, the actor-turned-politician said he rejected the donor’s offer. “I won’t be bossed, bullied, or bought,” he wrote.

Tlaib, the only Palestinian-American member of Congress, has faced intense scrutiny in recent weeks over her criticism of the Israeli government’s military operations against Hamas. Earlier this month, the House passed a GOP-led resolution to censure Tlaib over her comments.

Harper did not name the donor in the post. But in an interview with CNN, his campaign spokesman Karthik Ganapathy identified Michigan businessman Linden Nelson as the person who offered the financial support.

Nelson did not immediately respond to emails and telephone messages Wednesday afternoon.

Politico, which first reported on Harper’s allegation, said it had reached Nelson briefly but that he quickly ended the call and did not respond to subsequent messages seeking comment.

CNN reached Harper by phone Wednesday, but he referred questions to Ganapathy.

Ganapathy told CNN that Harper received Nelson’s call on October 16 and said it included an offer to bundle $10 million in contributions and provide another $10 million through independent expenditures on his behalf.

Candidates face strict limits on the size of donations they can receive from individuals, under federal law. And wealthy donors and the candidates they support are legally barred from coordinating financing for independent groups that can spend unlimited sums on a candidate’s behalf, said Saurav Ghosh, a former Federal Election Commission enforcement lawyer who now works with the Campaign Legal Center watchdog group.

But bundling together contributions that do not exceed the legal limits is permissible, he added.

Harper, a first-time candidate known for his roles on “The Good Doctor” and “CSI: NY” television shows, faces a stiff challenge in vying for an open Senate seat next year. Democratic Rep. Elissa Slotkin, another candidate seeking the Senate seat, had led Harper – and the rest of the field – in fundraising.

Harper is using the phrase about not being “bossed, bullied, or bought” to solicit campaign donations.

CNN’s Eva McKend contributed to this story.