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Former Congressman Tim Bishop this week endorsed Anna Throne-Holst as his preferred choice to challenge U.S. Representative Lee Zeldin for his former seat this fall.

Mr. Bishop, who served six terms as the East End’s congressman, credited Ms. Throne-Holst, the former Southampton Town Supervisor, as having proven her ability to build political bridges and navigate through sticky management problems.

“Over her years in public office, Anna has consistently demonstrated her ability to earn bipartisan support,” Mr. Bishop, who lost to Mr. Zeldin in 2014, said in a statement released by Ms. Throne-Holst’s campaign office this week. “She has demonstrated her ability to work productively in a divided government and has spent her entire career using her position to solve problems, two attributes that our current Congress desperately needs.”

Ms. Throne-Holst was a Southampton Town councilwoman for two years, and town supervisor for six and has regularly applauded Mr. Bishop, a Southampton native, for his responsiveness to the town’s needs during his tenure at the Capitol.

Ms. Throne-Holst has also been endorsed by Senator Kirsten Gillibrand and several other Long Island congressmen and has been championed by national Democratic Party officials as the preferred challenger to Mr. Zeldin, facing his first reelection bid.

Her primary opponent, David Calone, in contrast has seen many local Democrats align in his corner. All of the sitting Democrats on the East Hampton and Southampton town boards and Suffolk County Legislator Bridget Fleming, who sat next to Ms. Throne-Holst on the Southampton Town Board for six years, have endorsed him as their choice to be the party’s congressional nominee.

“Dave Calone is proud to have the endorsement of almost every Democratic elected official and party leader in our congressional district,” his newly appointed campaign manager Rahul Kale, said in a statement this week. “These local leaders understand that the best way to beat Lee Zeldin is to nominate a lifelong Democrat with a proven record creating jobs and who has consistently stood for protecting our environment.” Ms. Throne-Holst was officially registered with the Independence Party for most of her time in Southampton government, though she was endorsed by the Town Democratic Party in each of her election bids.

Mr. Calone, a businessman from Brookhaven and the former chairman of the Suffolk County Planning Commission, has also won endorsements from two major environmental groups: the Long Island Progressive Coalition and the Long Island Environmental Voters Forum.