WASHINGTON — Kamala Harris is launching a seven-figure ad blitz about health care targeting Donald Trump’s calls to replace the Affordable Care Act with a mystery plan he hasn’t yet released.

The ad campaign, first reported by NBC News, is aimed at elevating the issue and capitalizing on what polling says is a weakness for Trump. The new 60-second spot features Trump saying during his face-to-face debate with Harris that he has “concepts of a plan” to remake the U.S. health care…