Pittsburgh City Controller Michael Lamb withdrew from the city's mayoral race Monday, instead opting to endorse former Pennsylvania Auditor General Jack Wagner.

With five Democrats vying for the party's nomination before today's announcement, Lamb cited the need for clarity in a race that has been "muddied" since the March withdrawal of incumbent mayor Luke Ravenstahl.

"I don't want the conversation for our next leader to be generalities," said Lamb. "We need a real dialog to ensure we get the best possible candidate for the job."

Lamb said he thinks of Wagner as a thoughtful and independent candidate who "doesn't pander" and has strong relationships with organized labor groups. He said he believes that Wagner can beat frontrunner City Councilman Bill Peduto for the Democratic nomination, noting Wagner's experience as an independent executive in the state auditor general's office.

During a news conference at the IBEW union hall on the South Side Monday afternoon, Wagner thanked Lamb for the endorsement and declared their mutual respect.

Wagner said he's pleased with the progress of his young campaign.

"We've been in this race now three weeks, and we've gained considerable ground, more so than I even realized would be achieved in three weeks," said Wagner. "In the process, what I see is a unifying effort of many good people realizing the seriousness of the problems facing Pittsburgh."

City Council President Darlene Harris withdrew from the race last week, but has not yet endorsed another candidate. State Senator Jim Ferlo dropped out less than a week after filing petitions and endorsed Wagner last week. Lamb's departure Monday leaves four candidates on the ballot for the May 21 Democratic primary: Peduto, community activist A.J. Richardson, Wagner, and State Rep. Jake Wheatley (D-Allegheny).

Peduto issued the following statement regarding Lamb's exit from the race: "Voters have a clear choice to make. Pittsburgh needs a strong leader who has demonstrated a real commitment to ending waste, fraud, and abuse - someone who has revitalized neighborhoods and secured the city's finances."