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The administration’s loudest critics think not. “Biden Is Sending Our Treasures to Corrupt Oligarchs,” was the title of a Tucker Carlson screed on Fox News in early April, shortly before his own oligarch sent him packing. Vivek Ramaswamy, the Republican presidential candidate, has suggested that President Biden’s support for Ukraine is somehow connected to money his son got from the Ukrainian energy firm Burisma.

Such attacks, made in bad faith, are wildly overwrought. But they aren’t baseless. Last September, Ambassador Brink wrote a diplomatic cable warning the State Department of her concerns. “There are, for instance, severe limits on the number of American officials in the field and a number of security constraints on their movements,” Politico reported, summarizing Brink’s cable. “It’s also hard to find contractors willing to work in high-risk regions or set up in-person meetings with government officials, civil society leaders and others receiving the aid.” Both concerns echo the kinds of problems that plagued American aid efforts in Afghanistan.

A month after my visit to Ukraine, President Volodymyr Zelensky fired all of his top regional military recruiters following revelations of extensive bribery schemes. Then he fired his defense minister “as financial improprieties in the ministry came to light,” according to The Times’s Andrew Kramer. Ihor Kolomoisky, the oligarch who helped launch Zelensky’s political career, was arrested on suspicions of fraud and money laundering. Another Times investigation, into the former lawmaker Serhiy Pashinsky, showed the ways in which Ukraine’s desperate need for weapons in the early days of the war led to apparent profiteering by a dubious middleman. And U.S.A.I.D. still relies on the Beltway bandits to deliver goods.

Then, too, the sheer scale of money flowing into Ukraine makes it difficult to monitor. In a telephone interview, Jake Sullivan, Biden’s national security adviser, told me that $20.5 billion of the nearly $71 billion in total U.S. aid has gone to “direct-budget support” — much of it in the form of salaries for teachers, police officers, firefighters and other civil servants — in a “mechanism via the World Bank where the World Bank basically gets the receipts.” Given the bank’s mixed record on preventing corruption, that’s not completely reassuring.

Some of this, of course, is good news — evidence that Zelensky is willing to take political risks to confront corruption as none of his predecessors dared. It also suggests that the U.S. government is at least trying to learn from past mistakes. “We need to do a better job of impact analysis, randomized control trials, cash benchmarking,” Power acknowledged. “We are trying to systematize rigor around which programs are working and which are not.” The agency is doing more with local NGOs and independent media organizations to improve governance and accountability.