KIEV, Ukraine — The text message to Ukraine’s minister of economy and trade was as unwelcome as it was unexpected. The sender, a stranger, wrote that he wanted to be the new deputy minister.

The minister, Aivaras Abromavicius, a former investment banker from Lithuania, had joined the government amid promises by the new Western-backed leaders to clean up the country’s corrupt economy. Having no need or desire for a deputy, particularly someone he knew nothing about, Mr. Abromavicius tried to brush off the applicant.

“We don’t have the possibility to create a new position,” he wrote back.

“I think they will make one,” the man replied in another message, this one saved on the phone and released after Mr. Abromavicius resigned, in part over this exchange.

“I got this offer from the team of Petro Oleksiyovych,” the man wrote, referring to the country’s president, Petro O. Poroshenko. “Who specifically?” the minister asked.