Dan Pogorzelski, left, was leading Elizabeth Joyce Thursday in the race for a two-year term on the Metropolitan Water Reclamation District of Greater Chicago. [provided/Facebook]

Nine days after the June 28 primary, just one Chicago-area race remained too close to call on Thursday, but a late batch of mail-in votes tilted the result toward a clean sweep for the Cook County Democratic Party’s candidates for the $1.2 billion agency responsible for wastewater treatment and flood mitigation all over Cook County.

If Daniel Pogorzelski clings to his nearly 2,000-vote lead over Elizabeth Joyce through the end of ballot-counting next week, party-backed candidates will have successfully beaten back an insurgent slate led by an ousted former commissioner who argued he and his allies are more diverse and qualified than the party picks.