When Alan Black released a statement Tuesday endorsing Brian Trainor in the runoff race for district attorney of St. Tammany and Washington parishes, he cited Trainor’s experience and sympathy to Black’s platform as the reasons.

But on the eve of last week’s primary, Black — who finished third in the four-man field — apparently felt differently.

That night, he left Warren Montgomery — who would finish second to become Trainor’s opponent in the Dec. 6 runoff — a rambling voice mail, seeking to make sure that Montgomery still felt as he did: that should either of them not make the runoff, he would endorse the other because “the Trainor kid” had to be defeated.

A recording of that voice mail was played for The New Orleans Advocate on Tuesday night, just hours after Black announced his endorsement of Trainor.

“Hey, Warren, Alan Black here, just checking in, man,” the voice mail begins. Black says it was a “pleasure” running against Montgomery and that he wants to “make sure you and me are on the same page. If somehow you get there and I don’t, I want you to know I’ll be with you, me, my supporters, my family, my money, everything.”

Black then asks Montgomery to confirm that he reciprocates that feeling before saying he thinks “we’re uphill with Trainor. ... We’ve been against two law firms and the sheriff and a big machine.”

Trainor’s campaign has been closely linked with the Covington law firm of Talley, Anthony, Hughes and Knight, and Sheriff Jack Strain — for whom Trainor works as chief deputy — has been a vocal supporter of Trainor.

Black then says he is “glad to know that we’re all unified regardless that, uh, you, me and Roy (Burns, the other candidate in the race, who finished fourth) both all know that we just can’t let the Trainor kid win.”

Black then references a handshake deal he had with Montgomery to support each other in the runoff — something that Montgomery confirmed.

“I would just ask that we support one another if that opportunity comes and that we are not against one another,” Black says near the end of the message.

In an emailed statement Tuesday night, Black said the recording accurately reflected the way he felt during the campaign.

“The recording does not deviate from what I said during the campaign,” he said. “However, I took one week to talk with and evaluate both candidates. I changed my mind. It’s as simple as that.”

Montgomery and some of his supporters hint at more pragmatic reasons for Black’s switch. They point to a transcript of text messages between Montgomery and Black the day after the election, in which Black said he needed some time to think things through and mentioned that his campaign was “in the red.”

Black loaned himself at least $25,000 during the campaign.

Black said finances had nothing to do with his endorsement of Trainor.

“I simply needed time to talk to my supporters and to determine who would best support my campaign platform,” Black said in his emailed statement. “I met with Mr. Montgomery and Mr. Trainor, and both can tell you that my campaign finances were never discussed.”

Further, the timing of the recording’s release was “suspicious,” Black said.

The suggestion that there was some sort of financial deal for Black’s endorsement also provoked a strong denial from the Trainor camp.

“Any charge of this sort is absurd and not grounded in fact,” said Jay Connaughten, a Trainor spokesman. “It’s nothing more than sour grapes.”

At no time did anyone from the Trainor camp offer anything in return for Black’s endorsement, he said. Rather, he said, the two men have known each other for a long time, due in part to the fact that both are from Slidell.

Black’s endorsement, Connaughten said, was based on his evaluation of Trainor’s credentials as a former assistant district attorney and sheriff’s deputy, and on Trainor’s commitment to Black’s platform, including specialty courts and more resources for Washington Parish, where Black grew up.

Follow Faimon A. Roberts III on Twitter, @faimon.