“There’s definitely a shift on the Affordable Care Act from defense to offense,” said Representative Steve Israel of New York, chairman of the Democratic Congressional Campaign Committee. “Republicans have this political fantasy about repeal, but the facts of repeal are hard for people to swallow.” …

In Alaska, an outside group is running a commercial supporting the re-election bid of Senator Mark Begich, a Democrat, that features a breast cancer survivor running on the state’s snowy tundra as she talks about how Mr. Begich “fought the insurance companies so that we no longer have to.” In West Virginia, House Majority PAC recently bolstered Representative Nick J. Rahall II, considered a vulnerable Democrat, with an ad that talks about the protections that could be lost — such as the so-called black lung benefits for coal miners.

And a radio spot by Elisabeth Jensen, who is running in the Democratic primary in Kentucky to challenge Representative Andy Barr, criticizes Mr. Barr for repeatedly voting to repeal the Affordable Care Act. “We really have a good thing, and I think it’s time Democrats start standing up for it,” Ms. Jensen said in a phone interview, noting that Kentucky’s state health exchange was one of the more successful in the nation (she also said she was considering TV ads supporting the law as soon as she raised more money).