Legal scholar Steven Calabresi, in a generally accurate discussion of what Obama could do to change the federal courts, offers the following very strange argument:
This raises the question of whether Mr. Obama can in good faith take the presidential oath to "preserve, protect, and defend the Constitution" as he must do if he is to take office. Does Mr. Obama support the Constitution as it is written, or does he support amendments to guarantee welfare? Is his provision of a "tax cut" to millions of Americans who currently pay no taxes merely a foreshadowing of constitutional rights to welfare, health care, Social Security, vacation time and the redistribution of wealth? Perhaps the candidate ought to be asked to answer these questions before the election rather than after.
Aside from the issue of whether Obama meant to be saying the Constitution should be amended to change this (See this post and its comments for discussion of what Obama really meant), I find this argument extremely strange. The Constitution gives provisions for when it can be amended. If I swore an oath to uphold it, one of the things I would be upholding would be the legitimate amendment process that the Constitution specifies. A president could come along and advocate an amendment to the Constitution that changes it in extremely significant ways, but as long as due process for amending is followed it doesn't seem as if anything has been done to undermine the Constitution. What's been done is to undermine the moral principles behind why the Constitution is as if currently is, but it's not a violation of the oath to uphold the Constitution if you use the Constitution's own method of amending it to propose a change that's pretty drastic. It itself envisions that possibility.