Regulators in Delaware, Maryland, New Jersey and Virginia have all approved Exelon's proposal to acquire the Mid-Atlantic distribution utility Pepco.

But after multiple attempts, the District of Columbia still can't get behind the $6.8 billion merger.

On Friday, D.C. People's Counsel Sandra Mattavous-Frye rejected the latest deal, saying low-income customers wouldn't be protected from rate hikes under Exelon's plan. Mattavous-Frye's job is to represent the District's ratepayers.

“Most critical to me were the benefits for residential ratepayers, particularly low-income residents who struggle to pay their electric bills,” said Mattavous-Frye in a statement.

Last August, the District's Public Service Commission denied Exelon's plan to buy Pepco -- which would be one of the biggest utility acquisitions in history -- on the grounds that Exelon wouldn't do enough to promote renewable energy or improve Pepco's distribution operations.

“At a time of change in the energy field, Pepco’s ability to adapt will be constrained by an increased management bureaucracy," wrote commissioners.

Two months later, Exelon filed a motion to reconsider the acquisition, put together a settlement agreement with increased funding for local renewables programs, and seemingly convinced officials to go along with it.

Last month, the PSC rejected that agreement and issued a plan of its own. After months of lobbying, D.C. Mayor Muriel Bowser rejected the PSC proposal. She said it didn't do enough to protect ratepayers if Exelon took over Pepco's operations.

Exelon went back to the drawing board and revised its proposal once again. But Mattavous-Frye issued a statement today calling on the utility to set aside more money to protect ratepayers. 

The D.C. city government also rejected the latest proposal on Friday, but continues to support the settlement agreement Exelon filed last fall.

"It is really hard to imagine the deal going forward at this point," said Anya Schoolman, leader of the PowerDC Coalition, in an email. "We agree with the Office of the People’s Counsel’s filing. D.C. is ready to move on.”

It's unclear if Exelon will submit another plan. CEO Christopher Crane said he would give up on buying Pepco if he couldn't secure approval by March 4.

“If we can’t get it by March 4, then we have to fold up and then start to execute on the debt reduction and the buyback of the equity issued," said Crane.

Listen to our Energy Gang episode on the events that lead up to the initial rejection of the acquisition.