"We’re hoping that he will end up in the Senate. Exactly how that happens under Nebraska law is yet to be determined," McConnell said in an interview this week with CNN. "If that were the way it worked out, I think it’d be a smooth transition."

University of Nebraska-Lincoln professor Kevin Smith told Fox News Digital that "the Republican bench [to replace Sasse] would be pretty deep" given Nebraska's Republican bent. But Smith added that Ricketts is likely "the obvious choice" if the seat remains vacant past the end of his term.

Nevertheless, he said Sasse's announcement came as a surprise to observers from Lincoln to Capitol Hill.

"If this was planned and people knew about it, they kept that secret really well," Smith said.

Ricketts said in statement that he wouldn't appoint himself to the position when Sasse steps down, which, Fox News reported last week, is expected to happen in December.

"If I choose to pursue the appointment, I will leave the appointment decision to the next governor and will follow the process established for all interested candidates," Ricketts said in a Friday statement. "It is the honor of a lifetime to serve as the governor of Nebraska. It is the greatest job in the world, and it will remain my number one focus for the remainder of my term."

According to Nebraska Secretary of State Robert Evnen, Sasse's resignation would start a 45-day clock for the governor to pick a replacement. That means Ricketts, who is term-limited, could pass on making the appointment himself and let his successor make the choice in January. That successor is likely to be Pillen, who is favored in the general election after winning the primary.

Ricketts endorsed Pillen in the gubernatorial primary earlier this year over state Sen. Brett Lindstrom and Trump-endorsed Charles Herbster. Along with the endorsement, Ricketts gave $100,000 to Pillen's campaign.

Ricketts also donated $1.275 million to a group called Conservative Nebraska, an independent expenditure group that ran attack ads against Herbster and Lindstrom. Ricketts's father, Joe Ricketts, the founder of TD Ameritrade, also donated $150,000 to Conservative Nebraska, and his mother, Marlene, gave $100,000.

That totals more than $1.6 million from the Ricketts family to help Pillen in his primary, including $1.375 million directly from the governor. Meanwhile, Pillen's campaign overall raised slightly less than $9 million total, according to the latest numbers on the state website, meaning Ricketts' funding was a significant portion of the money spent on that primary.

Pillen eventually won a close race with just shy of 34% of the vote to Herbster's 29% and Lindstrom's 27%.

"The first the Governor heard of Senator Sasse’s plans to resign was last Thursday. He has never had a conversation with Jim Pillen about an appointment of any kind," Ricketts spokesperson Alex Reuss told Fox News Digital in a statement. "The Governor supported Jim Pillen because he was the best candidate to continue the conservative leadership the Governor has advanced over the past eight years."

"Jim Pillen is completely focused on becoming Nebraska’s next governor and helping Republicans win up and down the ballot on November 8th," a spokesperson for Pillen's campaign told Fox News Digital in a statement. "Ben Sasse is still one of Nebraska’s U.S. senators. Any discussion about an appointment to fill a vacancy that doesn’t exist is all hypotheticals and speculation."

"Jim found out about Sen. Sasse’s candidacy to lead the University of Florida at the time of his announcement, along with everyone else," the Pillen spokesperson also said. "He’s had no conversations with Gov. Ricketts or Sen. Sasse regarding a potential Senate vacancy."

Ricketts is notably a prolific donor to many GOP candidates and groups. According to Nebraska public records, Ricketts and his family have given more than $4.3 million to a wide variety of Republican candidates and groups in the state since the beginning of 2020. Ricketts has donated yet more money to out-of-state Republicans.