By now, you may have seen Charlie Cook's prediction that the Obama administration's push for health care reform will be like the Bush administration's push for war with Iraq. This strikes me as wildly off the mark. Wars and entitlements have entirely opposite life cycles in American public opinion.
Wars, as we know, tend to start off pretty popular. People rally around the president. And then the president gets a few months, maybe more, to finish things up. Bush Sr. knew that and deliberately chose a limited war strategy in Iraq in 1991 that would minimize the length of the conflict and maximize political support, both foreign and domestic. Longer wars, however, are costly for presidents, as Truman, Johnson, and W will attest.
By contrast, expansions of the social safety net tend to be initially divisive but very popular in the long run. Republicans in the 1930s blasted Social Security as socialistic. In the 1960s, Ronald Reagan (who by that point was comfortable with Social Security) compared Medicare to communism. No serious politician makes these claims today.
If the Democrats manage to pass health reform this year, this is likely to be a long term boon for the party, rather than a festering wound like Iraq.