The following exchange should give Republicans a pretty good indication of whether President Obama would rather have the upcoming election be focused on Obamacare or the economy:
White House reporter: "Friday, I believe, is the anniversary of the health care law, and I'm wondering if we should expect to hear from the president on that milestone, which of course is right before the Supreme Court arguments, or would he just assume not make a public statement about the health care law and let outside groups, the campaign and others, do the politicking around this moment?"
White House press secretary Jay Carney: "... The president is focused on doing everything he can, with Congress and independently, to help our economy grow and create jobs, to build an economy that's built to last and to make sure that we're doing everything we can in Washington to bring that about.
"The president does speak about health care on occasion and will continue to do that, but he is focused on a forward agenda right now, and working with Congress and doing the things he can through executive action to grow the economy and create jobs."
Why would Obama rather run on the economy? First, because it's likely to improve. Second, because—even if it doesn't—he can always try to shift the blame to President Bush or Republicans. But there's no shifting blame on Obamacare, the unpopular monstrosity that bears his name.