CALLICOON, N.Y. — Across New York’s Hudson Valley and points west, a sprawling demographic and cultural hodgepodge has emerged as a key battleground for the Democratic Party in its hope to flip the House of Representatives in November’s midterm elections.

More than $6 million has already poured into the race for the 19th Congressional District from Democratic donors. The only problem is that the Democrats have yet to settle on a candidate, and there are seven contenders, including two lawyers, a businessman and a former C.I.A. official.

“I’m staying neutral,” said Keith Kanaga, chairman of the Columbia County Democratic Committee. “Part of the thing we are all grappling with is that we like them all. But who will the general voter like the best? That’s turning out to be a hard question to answer. They are all attractive in different ways.”

There are not many districts that run more down the middle than the 19th District, which encompasses the Catskills and largely rural Otsego and Schoharie counties as well as much of the Hudson Valley. There are 141,000 registered Democrats, 138,000 Republicans and 115,000 independents.