The markets, known as exchanges, are a centerpiece of President Obama’s health care law, and running them will be a herculean task that federal officials never expected to perform. When Congress passed legislation to expand coverage two years ago, Mr. Obama and lawmakers assumed that every state would set up its own exchange, a place where people could shop for insurance and get subsidies to help defray the cost. But with Republicans in many states resisting the creation of exchanges or deterred by the complexity of the task, federal officials are preparing to do the job, with or without assistance from state officials. “We realize that not all states will be ready to establish these exchanges by 2014, so we are setting up a federally facilitated exchange in those states,” said Michael Hash, the top federal insurance regulator. “We are on track to go live in October 2013, which is the beginning of the first open season for the individual and small group markets.” Governors of 13 states with nearly one-third of the United States population have sent letters to the Obama administration saying they intend to set up exchanges. Complete applications are due on Nov. 16, just 10 days after the presidential election. Federal and state officials and health policy experts expect that the federal government will run the exchanges in about half of the 50 states — a huge undertaking, given the diversity of local insurance markets. The federal exchanges will vary from state to state. The Obama administration will not define a single uniform set of “essential health benefits” that must be provided by all insurers, but will allow each state to specify the benefits within broad categories. In running an exchange, federal officials face a delicate political task. They will encourage people to enroll, promoting the exchange as an important part of Mr. Obama’s health care overhaul. But they do not want to feed fears of a federal takeover or alienate state officials whose help they need. Much work will be done by contractors. With public opinion deeply divided over the new law, the Obama administration has invited advertising agencies to devise an elaborate “outreach and education campaign” to publicize the federal exchanges and their potential benefits for consumers. In addition, federal officials are looking for private contractors to provide “in-person assistance” to consumers and to operate call centers. A contractor will also help the government decide who gets federal subsidies, expected to average $6,000 a person, and who is exempt from the tax penalties that will be imposed on people who go without insurance. Federal officials have turned to the American subsidiary of a Canadian company, the CGI Group, to provide information technology services to the federal exchanges under a contract that could be worth $93.7 million over five years. An exchange is a sort of supermarket where people can compare prices and benefits of health plans offered by insurance companies. People will be able to file applications online, in person, by mail or by telephone. Mr. Hash, the director of the federal Office of Health Reform, said the federal exchanges “will operate essentially in the same manner as the state-based exchanges.” However, they differ in a significant way. States have done their work in public, but planning for the federal exchanges has been done almost entirely behind closed doors. “We have gotten little bits of information here and there about how the federal exchange might operate,” said Linda J. Sheppard, a senior official at the Kansas Insurance Department. “I was on a panel at Rockhurst University here, and I was asked, ‘Where is the Web site for the federal exchange?’ I chuckled. There really isn’t any federal exchange Web site.” Sabrina Corlette, a research professor at the Health Policy Institute of Georgetown University, said the federal exchanges were “much more opaque” than the state exchanges.