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Patricia Richardson is challenging Ken Howard for the presidency of SAG-AFTRA as the head of the Membership First slate, Variety has learned exclusively.

The “Home Improvement” star, currently a national board member, has selected stuntwoman Jane Austin as her running mate for the secretary-treasurer post.

Membership First has been quietly gathering signatures in recent days for its nominating petitions, which are due at 5 p.m. PDT on Friday.

Howard announced on June 1 that he would seek re-election with endorsements coming from George Clooney, Bryan Cranston, Betty White, Rita Moreno, Octavia Spencer, Ron Perlman, Clark Gregg and Josh Gad. SAG-AFTRA Los Angeles VP Jenny O’Hara joined Howard, running for secretary-treasurer as part of the Unite for Strength and United Screen Actors Nationwide slates.

Election ballots will be mailed to members who are paid up on dues on July 21 and tabulated on August 20. Turnout in the 2013 election — the first for the merged SAG-AFTRA — was about 20.5%, with ballots mailed to 139,967 eligible voters.

Howard, 71, has headed SAG-AFTRA since it was created three years ago and easily defeated Esai Morales — who headed the Membership First slate — and two other challengers in 2013.

Howard was first elected as SAG president, positioning himself as a moderate and pragmatist, in 2009 and re-elected in 2011. He won both times on a platform advocating for the merger of SAG and AFTRA, which was overwhelmingly approved by members despite active opposition from Membership First.

Richardson, 64, is best known for her role as Jill Taylor during the eight-year run of “Home Improvement” during 1991-99 and was nominated four times for an Emmy in the lead actress in a comedy series. She also starred in “Strong Medicine” between 2002-05 and had a recurring role on the 2005-06 season of “The West Wing.”

Austin, a longtime Membership First activist, was Morales’ running mate two years ago. In that election, the self-styled progressives of the Membership First faction, which controlled the SAG board room from 2005 to 2008, won only a handful of seats on the 70-member national board.

For the 28 open national board seats representing Los Angeles, the only Membership First candidates elected were Austin, Morales, Richardson, Martin Sheen, Joanna Cassidy and the late Sumi Haru. Sheen, who received the most votes of all candidates, was elected to a four-year term as were Austin, Cassidy and Morales.

Since the merger, SAG-AFTRA leaders have opted to keep a low profile during negotiations on the union’s master contracts and eschewed attempting to mobilize the membership in support of bargaining positions. In recent months, however, Howard has led an effort urging members to refuse non-union work.

For its part, Membership First has remained largely silent on issues, other than blasting national executive director David White last year for becoming a candidate to head the National Basketball Players Assn. during the run-up to SAG-AFTRA’s film-TV negotiations. The players union eventually selected attorney Michelle Roberts for the post.