The next president could be dealing with an ObamaCare insurer meltdown in his or her very first month. The incoming administration will take office just as the latest ObamaCare enrollment tally comes in, delivering a potentially crucial verdict about the still-shaky healthcare marketplaces. The fourth ObamaCare signup period begins about one week before Election Day, and it will end about one week before inauguration on Jan. 20. After mounting complaints from big insurers about losing money this year, the results could serve as a kind of judgment day for ObamaCare, experts say. “The next open enrollment period is key,” said Larry Levitt, senior vice president of the Kaiser Family Foundation. The Obama administration has struggled for several years to bring young, healthy people into the marketplaces, which is needed to offset the medical costs of older and sicker customers.