As expected, former city councilman Oliver Koppell will launch a primary challenge against Bronx Sen. Jeff Klein, the leader of a breakaway faction of independent Democrats.

The primary bid by Koppell is considered an uphill battle, considering that Klein is a prodigious fundraiser and has the backing of the Bronx political establishment.

Yet the primary underscores deep unrest within the Democratic advocacy base of the party in New York, which faults Klein and his Independent Democratic Conference for forming a power-sharing coalition with Republicans in the Senate.

The coalition, liberals argue, has helped to either block or water down progressive legislation in the Senate, ranging from the public financing of political campaigns and an increase to the state’s minimum wage.

“The moment Jeff Klein put Republicans in charge of the State Senate, he broke his word and betrayed the voters who elected him. We deserve better,” Koppell said in a statement. “Because of his actions, meaningful, progressive legislation that would improve the everyday lives of people across New York, has been watered down or blocked entirely.”

At the very least, the primary bid could prove to be a distraction to Klein, whose IDC has been supportive of a primary challenge from Erie County Legislator Betty Jean Grant agaisnt mainline Democratic Sen. Tim Kennedy of Buffalo.

In 2012, the IDC supported a primary challenge against Sen. Neil Breslin of the Albany area, who handily won.

Update: Klein spokeswoman Candice Giove sent along this statement.

“Senator Jeff Klein looks forward to a spirited debate of ideas and is eager to address his record of legislative accomplishments and his vision for the people of his district and for the future of this state.”