President Donald Trump tweeted Monday that he will not nominate businessman and 2012 Republican presidential candidate Herman Cain to a seat on the Federal Reserve.

"My friend Herman Cain, a truly wonderful man, has asked me not to nominate him for a seat on the Federal Reserve Board," Trump wrote. "I will respect his wishes."

In a blog post published later Monday, Cain explained his rationale for dropping out of consideration. Among them: The strict "ethical restrictions" that would constrain him from making money.

"I would have to let go of most of my business interests," he wrote. "I could not serve on any boards. I could not do any paid speeches. I could not advocate on behalf of capitalism, host my radio show or make appearances on Fox Business."

"Without getting too specific about how big a pay cut this would be, let’s just say I’m pretty confident that if your boss told you to take a similar pay cut, you’d tell him where to go," he added, noting that he "did like the idea of serving on the Fed!"

Cain continued, saying that as recently as last week he told Trump he was "all in" and was making plans to visit Washington, D.C., and meet with senators who expressed skepticism about his nomination.

"But the cost of doing this started weighing on me over the weekend," he said. "I also started wondering if I'd be giving up too much influence to get a little bit of policy impact."

Weeks ago, Trump announced that he was planning to nominate Cain, saying he recommended him "highly for the Fed."

"I've told my folks that that's the man," Trump added, noting that Cain was going through a background check "and I would imagine he would be in great shape."

But the needed support for Cain's possible nomination did not materialize in the Senate. Four Republicans — Sens. Kevin Cramer of North Dakota, Lisa Murkowski of Alaska, Mitt Romney of Utah and Cory Gardner of Colorado — indicated they were not in favor of his nomination, meaning that if all 47 Democrats were to vote no, Cain would not have the votes to be confirmed.

Cain made his name in the restaurant industry, where he ran the Nebraska-based Godfather’s Pizza franchise from 1986 to 1996 and has claimed his leadership saved the company from bankruptcy. He touted that experience as a conservative presidential candidate who was briefly the GOP front-runner in a crowded 2012 primary field.

But Cain ended his campaign after allegations surfaced that he had sexually harassed several women around the time he headed the National Restaurant Association from 1996 to 1999, and that he had an extramarital affair.

Cain has denied the allegations, and Trump called them an "unfair witch hunt."

Earlier this month, Cain posted a video to Facebook signaling that he might not make it through the confirmation process.

"You better believe that the people who hate me, who do not like conservatism ... are already digging up the negative stuff that are in stories from eight years ago," he said.

But the administration continued to insist his nomination was on track. In an interview with "Fox News Sunday" this month, acting White House chief of staff Mick Mulvaney said Cain's nomination was still alive and that he "would be a great member of the Fed."

Cain told The Wall Street Journal last week that he wouldn't withdraw his name from consideration.

Cain joined the Federal Reserve Bank of Kansas City in 1989, later becoming its deputy chairman and then chairman. In recent years, Cain tweeted favorably about raising interest rates — something Trump has repeatedly criticized the Fed for doing last year. Additionally, Cain has promoted a return to the "gold standard," where U.S. currency would be backed by gold.

Cain's withdrawal comes as Trump's most recent Federal Reserve pick, Stephen Moore, has come under fire for reports about his back taxes and failing to make alimony payments to his ex-wife.

Trump has taken aim at the Fed over much of the past year, repeatedly criticizing the institution for its monetary policies and stewardship of the economy under Chairman Jerome Powell, whom Trump nominated in late 2017.

Soon after news of Cain's withdrawal, Senate Minority Leader Chuck Schumer, D-N.Y., called on Senate Republicans to reject Moore as well.

"Herman Cain was woefully unqualified to be on the Federal Reserve and his failure to garner adequate support should not be used as a pathway by Senate Republicans to approve Stephen Moore, who is equally unqualified, and perhaps more political," Schumer said. "Mr. Moore, like Mr. Cain, poses a danger to the economic stability of our country."