Scattered fighting threatened a shaky cease-fire in eastern Ukraine on Sunday as officials now confront a task even more formidable than maintaining the truce: fashioning some form of decentralized governance in the war-ravaged region that President Vladimir V. Putin of Russia will accept and that President Petro O. Poroshenko of Ukraine can deliver without turning his country against him. But just two days after the truce was signed in Minsk, Belarus, calling for “decentralization of power” as the most important step after a halt to the violence, Yuri V. Lutsenko, an influential adviser to Mr. Poroshenko, published an article on Sunday denouncing the idea of creating a special autonomous zone in the east — which Russia has demanded — saying it would be “a cancerous tumor in the Ukrainian organism.” The article on the Ukrainska Pravda news site by Mr. Lutsenko, who is leading Mr. Poroshenko’s political […]