With the situation in Crimea having the potential to spiral out of control and Ukraine again emerging as a battleground between Russia and the West, the Obama administration may soon come to rue the expulsion of Viktor Yanukovych as president—unless his replacement is able to restore the balance between East and West, and in a fashion that can satisfy the expectations of the people of Ukraine for a more transparent, less corrupt government. After all, Yanukovych had campaigned on the promise that he would be more successful than his predecessor Viktor Yushchenko to link Ukraine to Europe economically while not burning bridges with Russia—and, as Adrian Karatnycky had noted when Yanukovych was first elected, "the signals emanating from Mr. Yanukovych's closest aides ... suggest the new president and the government he will try to bring into office will likely represent a broad-based mix of longtime Regions party officials, and competent financial and economic technocrats and market reformers." Instead, over time, Yanukovych became more authoritarian and corrupt in his ways—but there was one particular service his administration carried out on behalf of the United States.

The administration may not like to hear it—but its 'reset' with Russia which was lauded as one of its first term's triumphs—was facilitated in large measure by Yanukovych's election four years ago. The rhetoric about turning over a new leaf in U.S.-Russia relations was largely talk during 2009—an effort to change the tone—but with little substance to show for it.

But Yanukovych's narrow electoral victory in February 2010—followed by the decisions to stop Ukraine's efforts to seek NATO membership and to sign a long-term lease agreement providing for the Russian Black Sea fleet to remain at its bases in Sevastopol until 2042—changed the equation. Yanukoyvch "removed Ukraine from the chessboard of U.S.-Russia competition—and in turn decreased Russia’s need to cause problems for the United States in other parts of the world." From that point, the logjam broke and we began to see movement on improving U.S.-Russia relations. Moscow backed stronger sanctions against Iran, accelerated cooperation on the northern distribution network to Afghanistan (which proved to be a lifeline for the U.S. and NATO forces after Pakistan, in 2011, interrupted supply routes for a time), dropped its demands for explicit linkage of arms control to missile defense in the New START agreement (instead settling for symbolic language in the preamble), and, most significantly, chose not to use its veto to allow UN Security Council Resolution 1973 move forward which authorized the air campaign over Libya.

It would be a simplification to suggest that Yanukovych's accession to power was the only reason for improvement in U.S.-Russia ties after 2010—but certainly, the fact that Moscow and Washington were no longer engaged in a competition over Ukraine removed what had become an important source of tension during the second terms of George W. Bush and Vladimir Putin—destroying their initial rapprochement after 9/11. Those tendencies were held at bay for the first part of Obama's tenure—but after Putin returned to office, and protests broke out in Russia, a reset which had to some extent been predicated on having Dmitry Medvedev in the presidential chair to work began to falter.

What also changed with Putin's return to the presidency was the acceleration of the Eurasian Union—a project which had not been near and dear to the hearts of the team which surrounded Medvedev, which was counting on closer integration with the West to act as the motor for Russia's modernization. Growing out of Putin's earlier proposal for a "Single Economic Space" to re-integrate the economies of the former Soviet republics with Russia, the Eurasian Union was meant to be a much more encompassing economic—and to some extent political—commonwealth.

Yanukovych—and more importantly, the business oligarchs who backed him and bankrolled his party—were never particularly enthusiastic about Ukraine being absorbed into "Putin's EU", and wanted to hold Moscow's embrace at arm's length, while at the same time preserving their export markets in Russia and access to Russian energy. Earlier on, Russia seemed satisfied with having Ukraine maintain a looser association, but in recent months, the pressure began to grow for full-on Ukrainian accession—and part of the earlier bargain—that Ukraine would have to forego security-political links with the West (in terms of seeking membership in the North Atlantic alliance) but was free to pursue closer economic links with the EU—was altered. At the same time, the terms of the association agreement that Brussels was negotiating with Ukraine—in contrast to earlier accords sketching out a much vaguer partnership—would indeed foreclose on any possible Ukrainian association with the Eurasian Union.

Yanukovych had good domestic political reasons to dislike some of the provisions of the EU's agreement—particularly with relation to transparency, anticorruption and ending the use of judicial sanctions against ertswhile political opponents—but he had also campaigned in 2010 on the promise to bring Ukraine closer to Europe. The polling data indicated that Ukrainians had more than a 2 to 1 preference for the EU over the Russian-led Eurasian Union, so Yanukovych's decision at the last minute to forego traveling to Vilnius to sign the deal—combined with rising frustration over his authoritarian and corrupt ways—sparked the EuroMaidan movement.

The new administration (acting president Oleksander Turchynov and acting prime minister Arseniy Yatsenyuk) are calling for balance, arguing that Ukraine's "European choice" does not have to preclude good-neighborly relations with Russia, although it is clear that Moscow may not agree with that assessment.

U.S.-Russia relations weren't doing all that well over the last year—even if there was a glimmer of hope that the removal of chemical weapons from Syria might lead to cooperative efforts to reach a political settlement to the civil war—hopes dashed by the apparent failure of the second round of the Geneva talks. But there is absolutely no way I can see for compartmentalizing a serious dispute over Ukraine from impacting other parts of the U.S.-Russia relationship. This is why, after having seen the reset bloom, I warned in 2010 not take the apparent improvement in relations for granted, noting: "A shift in the political balance of power in Ukraine could easily put Kiev back in contention. The reset has bloomed—but whether these buds could survive a new, sudden frost remains to be seen." This now has come to pass.

Nikolas K. Gvosdev, a contributing editor at The National Interest, is a professor of national-security studies at the U.S. Naval War College. The views expressed are entirely his own.