YARDLEY, Pa. — Sitting at her pumpkin-decorated dining room table, Kristen Donnelly ticked off her top political concerns: pay equity for women, gun control and anti-immigrant sentiment. (Her husband of five years has a green card.)

As for the president? “I would never vote for Trump,” Ms. Donnelly declared.

An independent, and co-chair of the local chamber’s Women in Business committee, Ms. Donnelly, 35, is the kind of educated, affluent suburban woman whom Democrats are counting on to fuel a “blue wave” in November’s elections and sweep away the Republican majority in the House of Representatives.

Except that Ms. Donnelly plans to vote for Brian Fitzpatrick, the Republican congressman who represents Pennsylvania’s closely contested first district, north of Philadelphia.

“He’s definitely on the moderate side,” Ms. Donnelly said, praising his support for the nuclear family, the police department and “the idea that America as a nation is good, and that we can continue to protect the American experiment as it stands.”