Donald Trump announced on Friday that he would not debate Bernie Sanders, saying that he did not want to go one-on-one with the “second place finisher” in the Democratic contest and that the networks were not ponying up enough for the event.

“Based on the fact that the Democratic nominating process is totally rigged and Crooked Hillary Clinton and Deborah Wasserman Schultz will not allow Bernie Sanders to win, and now that I am the presumptive Republican nominee, it seems inappropriate that I would debate the second place finisher,” he said in a statement.

“Likewise, the networks want to make a killing on these events and are not proving to be too generous to charitable causes, in this case, women’s health issues. Therefore, as much as I want to debate Bernie Sanders —  and it would be an easy payday — I will wait to debate the first place finisher in the Democratic Party, probably Crooked Hillary Clinton, or whoever it may be.”

Trump seemed to agree to the prospect of a debate with Sanders in an appearance on “Jimmy Kimmel Live” on Wednesday, and then in a press conference on Thursday.

Sanders’ campaign sent out a statement on Friday saying that they had received two offers from broadcast networks — one was ABC — and that they included a “major contribution to charity.”

“We are prepared to accept one of those offers and look forward to working with the Trump campaign to develop a time, place and format that is mutually agreeable,” Sanders’ campaign said in a statement.

He is scheduled to appear on “The Young Turks,” the streaming show hosted by Cenk Uygur, on Friday afternoon. Uygur offered $1 million to charity if the two candidates agreed to debate on his show.

But many observers doubted that such a debate — unusual in that it pitted two contenders of opposing parties against each other, before the nominating contests were finished — would ever come to fruition.

“This whole thing started as a joke more than anything else, and I doubt that Trump was sincere in his acceptance, having given the matter zero thought,” said Alan Schroeder, a professor at Northeastern University and author of “Presidential Debates: 50 years of High Rick TV.” When Trump held a press conference on Thursday, he indicated that such a debate should raise a sum of $10 million to $15 million for charity. That, Schroeder said, was an indication “that he’s already back pedaling.”

Update: Sanders released a statement.

“In recent days, Donald Trump has said he wants to debate, he doesn’t want to debate, he wants to debate and, now, he doesn’t want to debate.

“Given that there are several television networks prepared to carry this debate and donate funds to charity, I hope that he changes his mind once again and comes on board.

“There is a reason why in virtually every national and statewide poll I am defeating Donald Trump, sometimes by very large margins and almost always by far larger margins than Secretary Clinton. There is a reason for that reality and the American people should be able to see it up front in a good debate and a clash of ideas.”