President Obama campaigned for reelection as a defender — and improver — of Medicare. Yet for all that he’s done as a health-care reformer, he hasn’t curbed spending on the government health-insurance plan for the elderly and disabled. Finding a fix has to be one of the most pressing issues on Obama’s agenda as he enters his second term. Will he increase Medicare’s eligibility age? Raise premiums for doctor’s visits? Craft some variation to Paul Ryan’s plan to turn Medicare into a voucher system? All options are on the table.