Exelon Corp's ambitious acquisition attempt to form the largest power generation firm in the U.S. may get a boost on Tuesday after a crucial vote at the annual shareholders meeting for NRG Energy, Inc in New Jersey.

Chicago-based Exelon, the largest U.S. nuclear power company, wants NRG shareholders to elect a proposed slate of four new directors to the NRG's board who will push for the acquisition.

Exelon's last offer was worth $7.5 billion, according to the Financial Times or 0.545 shares for each NRG share, an increase of 12 percent since its initial bid last October.

NRG has rejected Exelon's bid twice saying it undervalues the company.

In a separate vote, shareholders will decide on an Exelon proposal to expand the size of the NRG board to 19 members and elect an additional five Exelon-backed directors.

NRG’s current Board has condemned the proposals as inadequate and not in the best interest of NRG and its stockholders. NRG says Exelon is seeking to influence the Board to favor its hostile acquisition offer.

All four proxy advisory firms that counsel shareholders on how to vote have advised against Exelon's proposals for director's elections, Reuters reported.

Exelon Chief Executive John Rowe said last week in a statement, if none of its nominated directors were elected or only four did, Exelon would abandon its efforts to acquire NRG and go its own way. But it would press forward with determination in its bid if all nine of its directors were elected.