Who is most likely to destroy Social Security and Medicare?

Democrats cut $500 billion from Medicare and it is Republicans who are going to destroy it? With the huge deficits created by Democrats, that will be what threatens Social Security the most. If the deficits were still around $160 billion per year as they were the last year that the Republicans controlled both the Congress and the presidency, there would be much less of a threat to Social Security. I am hardly a fan of keeping Social Security or Medicare as they currently are, but it seems that the huge deficits that Democrats have created are what really endangers Social Security.