Alina Somova in the Mariinsky Ballet's production of ‘Swan Lake.’ (N. Razina)

It’s as though both of Russia’s major ballet companies have been caught in the unyielding grip of a polar vortex.

Bitter fissures have cracked through their elegant facades: Valery Gergiev, general director of St. Petersburg’s Mariinsky Theatre, comprising its opera and ballet, has been met with protests for his support of President Vladimir Putin, whose homophobic laws have galvanized not only gay athletes but the arts’ gay fan base. An abrupt shake-up at the renowned Vaganova Ballet Academy, feeder school of the Mariinsky, has further deepened anti-Gergiev sentiment in the ballet world.

Meanwhile, at Moscow’s Bolshoi Ballet, artistic director Sergei Filin was nearly blinded last year in a vicious acid attack instigated by one of his dancers. Pay-to-dance bribery allegations and an artist exodus ensued.

What a cruel business. What a relief that the art prevails. The Mariinsky’s “Swan Lake,” which began a week of performances Tuesday night at the Kennedy Center Opera House, scored a triumph for what is still proudly tender and harmonious in Russian ballet.

Watching “Swan Lake,” which lays bare a troupe’s collective technique and emotional commitment as no other ballet does, can amount to a chore if those dancing it aren’t excellent throughout the ranks. So many companies lack that kind of depth. Yet the opening-night cast led by Alina Somova and Vladimir Shklyarov drove home the argument that the Mariinsky is not one of them.

This ballet was alive with rare clarity and coherence. A kind of magic lit the stage from the first act’s deep autumnal landscape, a magic conjured by timing and breath and a shared aesthetic of grandeur. If these dancers are not to the manner born, they are to the manner trained, and you saw it in the way they heard the Tchaikovsky in the same way and moved cleanly on the same impulses. Prince Siegfried’s drinking companions, his virtuosic trio of friends, the bejeweled ensemble of well-bred young ladies — they all moved in rising and falling crests and interleaving patterns whose musical sensitivity simply astonished.

All of the order, privileged ease and controlled feeling of the court that Siegfried will one day inherit was made plain in the shape and flow of the dancing.

And then he throws it all away.

And we completely understand why.

How could he resist Somova’s Odette? Captive to a magician’s spell, she unspooled a magic of her own. Somova is known — and derided, by some — for her extreme flexibility more than her artistry, but it’s time for a reassessment. First of all, she is blessedly free of affectation: no Gothic dramatics, no face-pulling. Secondly, this whisper-thin, leggy creature who looks like a child has upper-balcony star quality. There is something fascinating and watchable about her, the way Joan Crawford was not a classic beauty but she made you focus on her every move, every minute.

Such half-beauties, half-curiosities achieve that fascination by creating tension, which keeps their audience alert. There is no mental coasting when you’re watching Somova. She has a strange, unsettling flying-apart quality. When launching into a big jump or a high kick, her limbs go in all directions; she seems as weightless as a paper doll. Where does the power come from to harness them again, and swiftly?

Later in the ballet, when she appeared as Odile, the black-hearted seductress who leads Siegfried to ruin, Somova began wobbling in her turns (Uh-oh! — train wreck coming) but darn if she didn’t suck herself up into a whirlwind that by the end of her solo felt like a force of nature. With power to burn: I’ve never seen an Odile whip off those punishing 32 fouette turns so fast, in such poor form —and so thrillingly.

Shklyarov was a fine and fitting prince, and endearingly young, like Somova. They looked like a couple of teenagers, which gave the whole production a feeling of freshness. They were not the only stars, however. The corps was the ballet’s moral center — the way the swan community surrounded Somova’s Odette in a clamor of compassion, and their piercing propulsion in all the weaving patterns and groupings of the lakeside scene under moonlight, amid trees hung with ice.

Alexey Repnikov conducted the Opera House Orchestra; luminous solos were given by concertmaster Oleg Rylatko and principal harpist Susan Robinson.

In an evening of many memorable moments, one of my favorites was a quick one, completed in a wink: When Siegfried realizes he has been tricked by Odile into betraying Odette, he is frantic, desperate and runs. . .to his mother, burying his face in her hands. So sweet! Tenderness and tradition meet in this cast, and it’s a splendid combination.

Mariinsky Ballet’s “Swan Lake”

continues at the Kennedy Center Opera House through Sunday with cast changes.