Both demonstrate that once a narrative is established in U.S. politics, it’s very hard to shake.

The proliferation and growing influence of social media can accelerate a news narrative, like these two stories, says Teddy Goff, who directed President Barack Obama’s digital strategy in 2012. Over time, however, social media also may help a countertheme prevail, he says. This has little to do with overhyped chatter about media bias. There are effective offsets to media partisanship: the Internet versus talk radio; Fox News versus MSNBC. The mainstream media’s only discernibly consistent bias is on cultural issues — abortion, gay rights, guns, race — while a smaller-movement conservative news media, oblivious to balanced or fair journalism, effectively pounds messages that often end up in the mainstream media.

That message pounding, coupled with the Obama administration’s miscues — the White House still resists tapping a chief executive officer to run the health-care initiative — has locked in, for now, a negative view of Obamacare. This despite some good news: More than 10 million Americans have new or better health-insurance coverage than before; health-care costs are moderating; and reforms such as prohibiting discrimination against people with pre-existing conditions are kicking in.

Optimists such as Tom Daschle, the former Senate Democratic leader, think that once the kinks are worked out, Obamacare will become popular, much as Medicare and the prescription drug plan for seniors did. Still, as he acknowledges, “It’s taking a long time for people to understand” that the benefits outweigh the problems. Democrats running in November don’t have a long time.