Former CIA officer Matt Castelli decried political extremism Tuesday, declaring victory as the Democratic candidate running in the state's 21st Congressional District to unseat U.S. Rep. Elise Stefanik.

Castelli defeated fellow Democrat Matt Putorti, leading with more than 80% of the vote with the majority of election districts reporting, according to the state Board of Elections.

"To all of you, I am so deeply grateful," Castelli said during a watch party at the Lawrence Street Tavern in Glens Falls. "This country-before-party campaign has been focused on our safety, our security and our strength."

He's running on the Democratic line and a third-party Moderate Party line on Nov. 8.

Castelli, who served as the director for counterterrorism in President Barack Obama's National Security Council, stressed the need to fight the rise of political extremism, inflation and high gas prices, and how to curb a rise in gun violence.

Castelli called out Stefanik, the third-highest GOP member in the U.S. House of Representatives, for failing to act during her eight years in office.

"We need a representative who's serious about solving them," he said.

To Stefanik, he had a clear message: "Watch out. We're coming for her."

Stefanik leads Castelli with a 10-1 cash advantage. In a statement, she said she welcomes Castelli's challenge.

"During far-left downstate Democrat Matt Castelli's limited interactions with voters who refused to debate in a Democrat primary, North Country voters have already learned that he is nothing more than another radical far-left downstate Democrat who fully supported Joe Biden and Lame Duck Speaker Pelosi's historic tax hikes, backs an assault weapons ban and thinks New York's bail reform "may be an effective solution,'" Stefanik said. "For these reasons, we are confident that NY-21 voters (which far-left downstate Democrat Matt Castelli became less than a month before launching his campaign) will soundly reject Castelli and re-elect Congresswoman Stefanik in another landslide victory this November so that she can continue her record of delivering real results for the North Country and upstate New York’s hard-working families, small businesses, farms, veterans and seniors."

It's anticipated to be one of the most closely watched congressional races this November.

Castelli led intelligence collection and counterterrorism operations serving in Afghanistan and Iraq, and worked within the unit that found Osama Bin Laden. He served as the director for counterterrorism on the National Security Council for the first year under former President Donald Trump's administration.