I'm not sure I understand your concern about Social Security nor your complaint about "the Democratic Left". As to the former, Social Security "spend[ing] 1.2% of GDP more than [it] collects over the indefinite future," while worrisome in theory, doesn't exactly lend itself to providing a compelling reason for fixing the program now. Over the years for which we can somewhat reasonably project the revenues and expenditures of the program (roughly fifty to seventy-five years into the future without any major discrepencies), Social Security remains solvent. Where does the compelling need to fix the problem now come from? (And I'm not advocating waiting until the last possible moment, I'm merely suggesting we can take our time to carefully consider the problem before rushing a "fix" through the political system.) As to "the Democratic Left", your argument appears to stem from a lack of care for the realities of politics. A Democratic politician appealing to a Democratic base that wants Social Security to remain largely untouched really would have to be a sucker to believe that he or she could gain votes by promising to change Social Security. The logic of Krugman et. al. is simple and has nothing to do with your WMD analogy: Social Security is not an immediate problem, and there are several immediate problems that need to be addressed in this election, so let's focus on those immediate problems.