Leach was considered the leading candidate in the party's primary for Pennsylvania's Seventh District, one of the most-watched races in the state.
Democrats have long believed that they have a shot at unseating Republican incumbent Pat Meehan, largely because President Trump lost the Delaware County-based district in 2016. The New York Times on Saturday reported that Meehan recently settled a sexual misconduct claim, which could make the race even more competitive.
In recent weeks, the Democratic Congressional Campaign Committee has searched for new candidates for the Seventh District, according to sources familiar with the group's thinking. Party leaders in the Philadelphia suburbs, who feel ascendant after winning some longshot local elections in November, have wondered what they should do next.
"Daylin was the front-runner, and when the front-runner drops out, people start asking questions: 'Who do you have?'" said David Landau, chairman of the Delaware County Democratic Committee.
Now, Clout has learned that a new candidate will throw her hat in the ring on Monday: Shelly Chauncey, a former officer for the Central Intelligence Agency.
She's got some party elites wondering: Can she fill the hole that Leach left when his campaign was turned upside down?
Chauncey, who lives in Glen Mills, has never run for office before. She said she worked for 15 years at the CIA, where she began as a secretary and moved up to work undercover in Latin America and East Asia. She "grew up on a small family farm" in North Carolina and is the "daughter of a prison guard and a teacher," according to an embargoed press release.
Chauncey, 37, said she decided to make a bid for the Seventh because she "can't sit back and watch our representative go to Washington and support an administration that's taking away our health care and destroying the equality of our education."
On paper, at least, Chauncey has qualities that many Democratic leaders want in candidates: She's a woman with a national security career and a working-class background. Joseph Sestak, the last Democrat to win the Seventh District, is a retired Navy admiral.
Landau said "the potential is certainly there" for Chauncey to become a top candidate. "She's very impressive. Let's see see in the next few weeks and months what she does."
One big, open question about Chauncey: Can she raise money?
Chauncey said on Friday that she was planning to meet with the DCCC over the weekend, and has been "in discussions" with EMILY's List. "They seem supportive and are offering their assistance."
A political insider in Delaware County also said "one or two" major Democratic donors have pledged their support to Chauncey. The Campaign Group, co-founded by Neil Oxman, is planning to do Chauncey's advertising.