In a post today, Ezra Klein pins such congressional abdications on polarization and divided government: “During periods of gridlock,” he writes, “Congress cedes power to other branches that would otherwise give it deference.” But I think the phenomenon is characteristic of our entire era, and not just the last few gridlocked years. Our presidents have claimed broad and ever-expanding national security powers not in the teeth of congressional opposition, but with tacit congressional assent — because Congress would rather not have to take responsibility for anything as fraught as a declaration of war, let alone whatever the N.S.A. is getting up to. Our courts have taken on an outsize role in debates over race and sex, religion and culture, because those are issues that most politicians are extremely uneasy tackling, debating, and voting on. Regulatory expansions (like today’s climate change proposals from the president) are embraced by liberal politicians as an appealing alternative to casting controversial votes for tax increases in the same spirit that pro-business judicial activism is embraced by conservatives as an alternative to casting controversial pro-business votes.

In some of these cases, Congress is ceding power out of incapacity, but just as often it’s ceding it by choice — deferring to the imperial presidency, welcoming the encroachments of the administrative state, looking to the juristocracy for refuge and support on difficult and polarizing issues. So while it’s worth criticizing judges for their immodesty and our presidents for their power grabs, it’s also important to recognize the role played by legislators whose abdications have enabled both: Politics abhors a vacuum, and our elected representatives are often far to happy to have someone else step in and fill it — as five justices did today, and may well do again tomorrow.