An offer is on the table to reunite the mainline Senate Democrats and the Independent Democratic Conference as the new State Senate majority, a source with knowledge of the offer tells City & State.

The offer came together yesterday at a secret meeting in New York City that included Gov. Andrew Cuomo, New York City Mayor Bill de Blasio, State Senate Majority Coalition Co-Leader Jeff Klein and representatives from several of the state’s most powerful unions. According to City & State’s source, who spoke on the condition of strictest anonymity so as not to anger the parties involved, under the terms of the agreement Klein would continue as co-leader of the Senate with a representative of the mainline Democrats—presumably either Senate Minority Leader Andrea Stewart-Cousins or State Sen. Michael Gianaris, the leader of the Senate Democratic Conference’s campaign committee—replacing current Coalition Co-Leader Dean Skelos, the Senate Republican leader.

If the deal is accepted by all of the parties involved it would instantly bring about a profound sea change in New York politics, potentially deposing the Senate Republicans from power next session and moving the state farther to the left. It would also open up the possibility for a slew of progressive legislation to pass that has been stymied up to date as a result of opposition from the State Senate Republicans.

While it is not clear what would become of the electoral challenges to Klein and Tony Avella, one of the five members of the IDC, the source said that the current understanding is that the institutional support for Klein’s challenger, former State Attorney General and New York City Councilman Oliver Koppell, and Avella’s opponent, former New York City Comptroller John Liu, would evaporate, forcing Koppell and Liu to either drop their bids or fend for themselves against a reunited Democratic Party.

An agreement between the two factions of Senate Democrats, which split in 2011, would also have a significant effect upon both the standing of Gov. Cuomo and Mayor de Blasio. A deal would mean that Cuomo would have made good on his promise to the Working Families Party to use his clout to bring the IDC back into the fold, in exchange for the party giving him its line and backing his reelection bid this November. As for de Blasio, it would cement his status as the foremost progressive in the state and affirm his growing reputation as a powerbroker with the ability to unravel political enigmas no one else could solve.

The governor’s office and Mayor de Blasio’s office did not immediately return calls and emails seeking comment, and a spokesperson for the Independent Democratic Conference declined to comment.