Ronald Reagan and Bill Clinton had approval ratings of about 43% at this point and went on to crush their opp?

I don't understand why Republicans are quickly jumping to conclusions about the fate of Obama's Presidency. Both Clinton and Reagan had walked in on bad recessions their first terms. The economy didn't start crawling out of both holes until the very end of both their first terms. Why are republicans under the assumption that Obama can and should be able to fix everything, in a even worse Recession faster than Reagan and Clinton?