State Sen. Katherine Clark, one of five Democratic candidates running in an upcoming special election primary in Massachusetts’ 5th District, received the endorsement of EMILY’s List on Friday, less than a month out from the Oct. 15 contest.

An endorsement from EMILY’s List will likely provide Clark with a flush of cash and organizational help going into this crowded primary in which organization will be key to success.

The EMILY’s List endorsement is notable as the organization which seeks to boost progressive women into elected office chose Clark over another Democratic woman in the race: state Sen. Karen Spilka.

“Katherine Clark has an impressive record fighting for women and families in her community, and her effective leadership is exactly what Washington needs,” EMILY’s List President Stephanie Schriock said in a release. “From the school committee in Melrose to the state Senate in Boston, Katherine has been a champion for children and has put the safety of Massachusetts families first. … The EMILY’s List community — now more than two million members strong — is excited to continue supporting Katherine’s strong campaign, so that she can block Republican extremists from attacking women’s rights and opportunities and move our country forward.”

The special election was called after Edward J. Markey was sworn into the Senate, after winning a Senate special election this spring.

Other candidates in the race include state Sen. William Brownsberger, Middlesex County Sheriff Peter Koutoujian and state Rep. Carl Sciortino.

Massachusetts’ 5th District is rated a Safe Democratic contest by Rothenberg Political Report/Roll Call. Whoever wins the Oct. 15 Democratic primary will likely be the next member of Congress from the district.