There are now serious questions about whether Mr. LaCour achieved the high response rate he claimed. He has acknowledged that he did not pay participants as he had claimed, according to Dr. Green and Dr. McNutt, the Science editor in chief. In a letter that he sent through his lawyer, Dr. McNutt said, Mr. LaCour said he had instead allowed participants the chance to win an iPad, saying “that was incentive enough.” Dr. McNutt said the supposed payments had convinced the reviewers that the response rate was as high as the study reported.

He was a graduate student who seemingly had it all: drive, a big idea and the financial backing to pay for a sprawling study to test it.

In 2012, as same-sex marriage advocates were working to build support in California, Michael LaCour, a political science researcher at the University of California, Los Angeles, asked a critical question: Can canvassers with a personal stake in an issue — in this case, gay men and women — actually sway voters’ opinions in a lasting way?

He would need an influential partner to help frame, interpret and place into context his findings — to produce an authoritative scientific answer. And he went to one of the giants in the field, Donald P. Green, a Columbia University professor and co-author of a widely used text on field experiments.

“I thought it was a very ambitious idea, so ambitious that it might not be suitable for a graduate student,” said Dr. Green, who signed on as a co-author of Mr. LaCour’s study in 2013. “But it’s such an important question, and he was very passionate about it.”

Last week, their finding that gay canvassers were in fact powerfully persuasive with people who had voted against same-sex marriage — published in December in Science, one of the world’s leading scientific journals — collapsed amid accusations that Mr. LaCour had misrepresented his study methods and lacked the evidence to back up his findings.

On Tuesday, Dr. Green asked the journal to retract the study because of Mr. LaCour’s failure to produce his original data. Mr. LaCour declined to be interviewed, but has said in statements that he stands by the findings.

The case has shaken not only the community of political scientists but also public trust in the way the scientific establishment vets new findings. It raises broad questions about the rigor of rules that guide a leading academic’s oversight of a graduate student’s research and of the peer review conducted of that research by Science.

New, previously unreported details have emerged that suggest serious lapses in the supervision of Mr. LaCour’s work. For example, Dr. Green said he had never asked Mr. LaCour to detail who was funding their research, and Mr. LaCour’s lawyer has told Science that Mr. LaCour did not pay participants in the study the fees he had claimed.

Dr. Green, who never saw the raw data on which the study was based, said he had repeatedly asked Mr. LaCour to post the data in a protected databank at the University of Michigan, where they could be examined later if needed. But Mr. LaCour did not.

“It’s a very delicate situation when a senior scholar makes a move to look at a junior scholar’s data set,” Dr. Green said. “This is his career, and if I reach in and grab it, it may seem like I’m boxing him out.”

But Dr. Ivan Oransky, A co-founder of “Retraction Watch,” which first published news of the allegations and Dr. Green’s retraction request, said, “At the end of the day he decided to trust LaCour, which was, in his own words, a mistake.”

Many of the most contentious particulars of how the study was conducted are not yet known, and Mr. LaCour said he would produce a “definitive” accounting by the end of next week. Science has published an expression of concern about the study and is considering retracting it, said Marcia McNutt, editor in chief.

“Given the negative publicity that has now surrounded this paper and the concerns that have been raised about its irreproducibility, I think it would be in Michael LaCour’s best interest to agree to a retraction of the paper as swiftly as possible,” she said in an interview on Friday. “Right now he’s going to have such a black cloud over his head that it’s going to haunt him for the rest of his days.”

Only three months ago he posted on Facebook that he would soon be moving across country for his “dream job” as a professor at Princeton. That future could now be in doubt. A Princeton spokesman, Martin Mbugua, noting that Mr. LaCour was not yet an employee there, said, “We will review all available information and determine the next steps.”

Critics said the intense competition by graduate students to be published in prestigious journals, weak oversight by academic advisers and the rush by journals to publish studies that will attract attention too often led to sloppy and even unethical research methods. The now disputed study was covered by The New York Times, The Washington Post and The Wall Street Journal, among others.

“You don’t get a faculty position at Princeton by publishing something in the Journal Nobody-Ever-Heard-Of,” Dr. Oransky said. Is being lead author on a big study published in Science “enough to get a position in a prestigious university?” he asked, then answered: “They don’t care how well you taught. They don’t care about your peer reviews. They don’t care about your collegiality. They care about how many papers you publish in major journals.”

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