President Poroshenko’s failure to move ahead with reforms or to resolve decisively the political crisis in Ukraine has dismayed his U.S. partners. That made for a difficult visit to Washington.

Ukraine’s Prime Minister Arseniy Yatsenyuk has been under pressure to resign, but unexpectedly lived to fight another day after a parliamentary vote of no-confidence against him failed. What lies behind his political survival?

Poroshenko must rely on a patchwork of political alliances that are alternately cooperative and confrontational. If he begins investigating officials — whether from the Yanukovych regime or otherwise — he will quickly face an army of new enemies and upset the fragile balance that allows him to remain in power.

The merger of President Poroshenko’s party with the UDAR party of Kiev mayor Vitali Klitschko is another step in the consolidation of power by the Ukrainian leader. Arseniy Yatsenyuk’s People’s Front may be the next in line for absorption. But recent Ukrainian history shows that these big united parties have all ended in failure.