MARTINEZ -- Contra Costa District Attorney Mark Peterson has reached a tentative settlement with a deputy DA who's suing her employer on allegations that she was retaliated against for supporting Peterson's opponent in the 2010 election.

Attorneys for Peterson and prosecutor Jill Henderson agreed to the undisclosed settlement on Monday morning, thereby canceling the start of a Contra Costa County merit board hearing on Henderson's political-retaliation claim that's been proceeding separate from her lawsuit.

The proposed settlement goes to the Board of Supervisors for consideration Oct. 16. If the board approves it, the terms will be made public, and both Henderson's pending federal lawsuit and her merit board claim will be dismissed, attorneys in the case said.

Henderson, a 14-year veteran with the office, and Lucinda Simpson, a former Contra Costa prosecutor, each filed federal lawsuits against Peterson and the county in late September. A third prosecutor, former Richmond branch manager David Brown, was the first to sue Peterson in April.

Brown and Henderson separately allege that they were transferred to unfavorable assignments traditionally reserved for junior attorneys in retaliation for supporting local attorney Dan O'Malley in the contentious 2010 District Attorney race. Simpson, who quit the office before the election, alleges she was not rehired in favor of a less-experienced Peterson supporter because of her O'Malley campaign work.

Peterson has said all three lawsuits are without merit and that he has promoted numerous O'Malley supporters since he took office in January 2011.

Henderson's lawsuit also alleges that Peterson retaliated against her for supporting a former Contra Costa prosecutor who accused deputy DA Michael Gressett of rape in 2008. A judge dismissed the criminal indictment because the state didn't tell the grand jury that the accuser obtained a $450,000 settlement from the county, and now Gressett is suing the county and investigators for malicious prosecution.

Henderson further alleges that she and other women in the District Attorney's Office suffer ongoing gender discrimination that has been part of the office culture since long before Peterson took office.

Henderson's merit board hearing, however, was only to cover the political-retaliation allegations. If supervisors reject the settlement, the merit board hearing will be back on, with numerous current and former prosecutors subpoenaed to testify and thousands of emails to Peterson from his management team introduced into evidence.

Contact Malaika Fraley at 925-234-1684. Follow her at Twitter.com/malaikafraley.