Michael Tesler finds “that public perceptions of the debt’s importance are fundamentally linked to which party is making it an issue”:

Back in December 2007, politically attentive Democrats were 20 percentage points more likely than politically attentive Republicans to say that the federal budget deficit was at least a very important issue. Four years later, though, the most politically attentive Republicans were now a whopping 60 points more likely than their Democratic counterparts to say the deficit is very important.

Yglesias adds:

[I]t’s crucial to understand that the flip-flopping happens with the best-informed people not the worst-informed people. If you’re well-informed you gain a lot of information about “your side’s argument” on the issues of the day and map your opinions to the shifting political currents.

Update from a reader:

I’m sure lots of people are emailing you about this today, but I figured I’d jump in anyway. We were in a very different place in the economic cycle in 2007 and 2011. Basic Keynesianism tells us that deficits are problematic when the economy is at full output but necessary during demand-driven recessions. It’s certainly true that Democrats are more likely to be Keynesians than Republicans, but that doesn’t make the change of opinion flip-flopping. It makes it an informed application of a consistent theory in changing circumstances. Yglesias got serious flack in his comments section for the post you quoted from, for this very reason.