Former state Assemblyman Paul Tonko, one of the leading Democratic candidates in the race to replace retiring Rep. Mike McNulty (D), picked up the endorsement Tuesday of the Working Families Party, a small but influential third party in New York with close ties to organized labor.

The endorsement could give Tonko organizational momentum as he heads toward the Sept. 9 Democratic primary with Albany County Legislator Phil Steck, Tracey Brooks, a former top aide to Sen. Hillary Rodham Clinton (D-N.Y.), and others.

“The Working Families endorsement is a seal of approval,” Karen Scharff, chairwoman of the party’s Capital Region chapter, told the Albany Times Union. “It says: Paul Tonko will fight in Washington for working people.”

Meanwhile, a 10th Democratic candidate entered the race this week. Joseph Sullivan, a former chairman of the Albany City Republicans who switched parties three years ago, cast himself as a conservative Democrat who will emphasize national security.

Also this week, Sen. Charles Schumer (D) said he would not endorse a candidate in the crowded primary because he has so many “friends” in the race.

— Josh Kurtz