Mr. Putin, 67, has already been president or prime minister for 20 years, and Russia’s Constitution requires him to step down after his current term ends in 2024. Most Russians expected Mr. Putin, a former K.G.B. spy, to stay in power anyway; the question was how he would justify it.

What’s next: Mr. Medvedev’s replacement is a virtually unknown technocrat, and it’s unclear if the resignations on Wednesday signal a rift in Russia’s political elite or a coordinated plan to reshape the system. Here are six takeaways.

Quotable: “Why has this all happened in a single day?” one Russian reporter asked on Twitter. “It just means that those in Kremlin know history well: revolution has to be made swiftly, even if it’s a revolution from above.”

Go deeper: With America and Europe in tumult, Russia is punching above its weight despite a sputtering economy.