Interviews with two dozen contractors, current and former government officials, insurance executives and consumer advocates, as well as an examination of confidential administration documents, point to a series of missteps — financial, technical and managerial — that led to the troubles…

One person familiar with the system’s development said that the project was now roughly 70 percent of the way toward operating properly, but that predictions varied on when the remaining 30 percent would be done. “I’ve heard as little as two weeks or as much as a couple of months,” that person said. Others warned that the fixes themselves were creating new problems, and said that the full extent of the problems might not be known because so many consumers had been stymied at the first step in the application process.

Confidential progress reports from the Health and Human Services Department show that senior officials repeatedly expressed doubts that the computer systems for the federal exchange would be ready on time, blaming delayed regulations, a lack of resources and other factors…

One highly unusual decision, reached early in the project, proved critical: the Medicare and Medicaid agency assumed the role of project quarterback, responsible for making sure each separately designed database and piece of software worked with the others, instead of assigning that task to a lead contractor…

By early this year, people inside and outside the federal bureaucracy were raising red flags. “We foresee a train wreck,” an insurance executive working on information technology said in a February interview. “We don’t have the I.T. specifications. The level of angst in health plans is growing by leaps and bounds. The political people in the administration do not understand how far behind they are.”