PRESIDENT OBAMA and German Chancellor Angela Merkel sounded firm at the beginning of this month when they warned that disruption of Ukraine’s election by Russia would trigger a tough new round of sanctions by the West. The White House subsequently offered an expansive definition of what it meant by “disruption,” saying it would judge not just whether Moscow’s agents tried to stop voting, but whether the government of Vladimir Putin tried to prevent such interference.

As Ukrainians prepared to head to the polls Sunday it was evident that there would, in fact, be substantial disruption of the vote in the two provinces where militants under the command of Russian operatives have seized government buildings and declared independent republics. Ukraine’s largest election monitoring organization said that in 23 of the 35 election districts in Donetsk and Luhansk provinces, which contain 15 percent of Ukraine’s electorate, no voting would be possible because of a violent campaign by the militants, who have abducted and threatened election commissioners, ambushed Ukrainian security forces and ordered voters to stay home.

There’s little question among Ukrainian government officials and Western diplomats in Kiev that Russia is backing the separatists and has done nothing to stop their interference. Yet U.S. and German officials were saying before the vote that the sanctions they threatened would not be adopted unless the disruptions spread elsewhere in the country or Russia took more overt action to block the election. Once again the goalposts for measuring when steps to stop Mr. Putin are mandated appear to have been moved back.

Officials justify the retreat by pointing to the likelihood that the election will proceed smoothly in the rest of the country. They note that Mr. Putin on Friday hinted he would accept the results. While Russia has yet to fulfill its repeated promises to withdraw the tens of thousands of troops on Ukraine’s border, the Pentagon now says a small number may have moved back.

Western governments appear to be hopeful that a victory in the presidential vote by Petro Poroshenko, the business magnate who is far ahead in polls, could encourage Moscow to reach an accommodation with the new government. With extensive business interests in Russia, Mr. Poroshenko, who held posts in several previous Ukrainian governments, is well known to Mr. Putin. But such optimism seems less the product of sound analysis than of necessity. European Union governments have been unable to agree on the makeup of a new sanctions package, and the Obama administration declines to act independently of its allies.

The bottom line is that Mr. Putin could come out of the election having kept alive the separatist movement in eastern Ukraine without suffering economic consequences. He will be able to keep demanding that any political settlement give Moscow de facto suzerainty over the eastern provinces and the power to block any move by Ukraine toward the West. Mr. Poroshenko has pledged to quickly sign an E.U. association agreement and to put down the separatists by force. The latest lapse of Western resolve may cause him to wonder if he will have to face Russian aggression alone.