Screen shot/ Joe Manchin campaign

Democrats are pretty optimistic about their chances of gaining a majority in the House this November—and with good reason. But the Senate is another matter. Dan Balz did a good job of explaining why.

Republicans are only defending nine of the 35 Senate seats up in November. They have to play far less defense than the Democrats. Second, many of the most competitive Democratic-held seats are in states Trump won easily in 2016: West Virginia by 42 points; North Dakota by 36 points; Montana by 20 points; Indiana and Missouri each by 19 points.

There is an interesting theme that is taking shape among those Democratic incumbents running in deeply red states, as is evidenced by this new ad from Joe Manchin in West Virginia.

Almost a month ago Heidi Heitkamp, who is running for re-election in North Dakota, released this ad:

We’ve seen similar things from Claire McCaskill in Missouri, Jon Tester in Montana, and Joe Donnelly in Indiana.

It might not seem remarkable that Democratic Senators, even in red states, are defending Obamacare’s pre-existing conditions provision. But the truth is that supporting Obamacare was once a liability for some, with a study suggesting that 13 Democrats lost their seats in 2010 because they voted in favor of the Affordable Care Act. That was still the conventional wisdom in the 2014 midterms when Thomas Edsall wondered if Obamacare was destroying the Democratic Party.

As a testament to how much things have changed, we’re now seeing Democrats in some of the reddest states in the country putting support for provisions of the ACA front and center in their campaigns. Of course they’re not calling it “Obamacare,” or even referring to it as the “Affordable Care Act” because those words can trigger negative reactions. But you know how far we’ve come when Joe Manchin is aiming his shotgun at attempts to unravel the protections in Obamacare that Americans have come to rely on.