Russia could engineer a coup in Ukraine out of sheer nervousness and lack of better ideas, in the vague hope that the Eurasian dream can somehow be rescued for Mr. Putin. But if and when the Russian puppets fail, Mr. Putin would face a choice between armed intervention and loss of face. The use of Russian arms in Ukraine would probably lead to massive bloodshed, but not to a favorable outcome for Moscow. Even if Russia could win a quick war, which is unlikely, underground resistance would continue.

The European Union and the present Ukrainian leadership must strike a deal — and quickly. The remaining dictatorship laws must be repealed and a full amnesty granted to opposition activists. International organizations such as Doctors Without Borders should be given a list of those arrested and allowed to visit the wounded. Parliamentary democracy should be restored on the model of the 2004 Ukrainian Constitution, and new presidential and parliamentary elections must be held. The way out of the crisis is a return to Ukrainian democracy. Mr. Yanukovych was elected, but has since illegally changed the system in ways that undermine its legitimacy.

With a fresh start and new elections, Ukrainians could decide for themselves whether they prefer Europe or Eurasia. From its side, the European Union could renew talks over an association agreement, and offer some immediate loans. If democracy is restored in Ukraine, the Ukrainian economy would no doubt be hurt by the end of Russian loans and by Russian trade boycotts. But European countries can buy whatever products Russia boycotts and, in the long run, trade with Europe is more important than trade with Russia.