Idaho on Saturday becomes the latest state to launch its own health insurance exchange under the federal health law, with marketplace officials promising an easier shopping experience for consumers and greater responsiveness to insurance agents. But the exchange, yourhealthidaho.org, will be challenged to do as well as the federal insurance exchange during the first open enrollment period that ended last March. About 76,000 Idahoans signed up for private coverage at healthcare.gov, one of the most successful enrollments in any state. Idaho will be one of a dozen states, along with Washington, D.C., to run its own online marketplace this year — and the only one whose state government is completely controlled by Republicans.