SPRINGFIELD — Kimberly Lightford’s vote for a white candidate for Illinois Senate president over a fellow African American politician — 11 years ago — may have helped cost her this year’s Senate president’s job on Sunday.

After hours of tense, behind-the-scenes negotiations between lawmakers on Sunday, Lightford lost out to Sen. Don Harmon, D-Oak Park, who will replace retiring Senate President John Cullerton.

Publicly, party leaders made a show of unity. Lightford, who is Senate majority leader, hugged Harmon on the Senate floor Sunday afternoon as she nominated him to become the next Senate president. Harmon, who is white, was elected unanimously after hours of negotiations.

But afterward, accusations flew of personal betrayal, and longtime simmering feuds bubbled over.

Lightford, D-Maywood, blamed former Illinois Senate President Emil Jones Jr., and his son, Emil Jones III, who is currently in the Senate, for her loss. She would have been the first female black Senate president. She thinks their opposition may stem from an 11-year-old grudge.

In 2009, Lightford voted for Cullerton, the white candidate, for Senate president, over Sen. James Clayborne Jr., who is black.

Lightford claims Jones III, D-Chicago, acted as a double agent, calling what he did a personal betrayal. Lightford claimed the elder Jones, 84, also helped to steer votes away from her, a claim he denied to the Sun-Times on Sunday.

Lightford said since “I didn’t vote for Clayborne,” the elder Jones put his son “up to making sure that I didn’t become Senate president.”

Lightford said she never felt respected by the elder Jones.

“I never did anything negative to Emil Jones. He was a much older man, like my grandfather’s age. And I just think he had an issue with women and never supported me.”

“I never voted against him, even when he was treating me bad. So now you want to come and give me this payback and use your son as a vehicle to do it?”

Reached Sunday night, the elder Jones denied he got involved in the race or that his son voted for Harmon over bad blood.

But he brought up Lightford’s vote for a white candidate over a black one in the 2009 Senate president election.

“I don’t know how you can come back and say I want the black support when you had that opportunity to support the black and you didn’t,” the elder Jones said.

Lightford told reporters Jones III betrayed her by telling her he would support her but in fact worked behind her back by informing Harmon’s camp of her moves and drumming up support for Harmon.

Lightford said she had just left Jones III’s house Friday night when his support for Harmon went public by a news release.

When Emil Jones III came into the Senate, “I always treated him really, really well and I wanted him to see that ‘I can mentor you and be there for you in ways that your father wasn’t for me,’” Lightford said.

Lightford said Jones III is a familiar face at family functions.

“He’s been just part of my family. So it was emotional for me in that it was heartbreaking — because it’s OK to vote for someone else . . . But it’s not OK when you appear to be a part of my family and you lie.

“And he kept the Senate Black Caucus divided the entire time,” said Lightford, who heads the Illinois Legislative Black Caucus.

Lightford said Jones III’s role in the process was discussed during negotiations with Harmon earlier Sunday. She said she and others demanded that Jones III remain out of leadership and said Harmon agreed. Lightford said the riff had nothing to do with her relationship with Harmon.

“We talked to him because that was a part of our negotiations. That he can’t be representing us in leadership if he has behavior such as that,” Lightford said.

By mid-afternoon, Jones III exited the private caucus to update reporters. He was asked if he would be getting a leadership position because of his support for Harmon and said no.

Reached Sunday evening, Jones III said he told Lightford on Friday night he would support Harmon. He also told her he would resign as co-chair of the Illinois Senate Black Caucus.

Jones III denied that he voted for Harmon over any bad blood.

“Leader Lightford stated that she had certain votes and me reaching out to those members directly, they told me otherwise,” Jones III said.

Jones III downplayed that he won’t get a leadership post, despite helping bring votes to Harmon.

As for Lightford’s claims of payback, Jones III suggested Lightford hadn’t been straight with him: “A friend would not let you go down on a sinking ship. If your ship is sinking and you know it’s sinking, let your friend know.”