Are lower mortgage rates the answer?

As a first-time home buyer, I love the idea of the government stepping in and lowering mortgage rates to 4.5% by fiat. But is it the solution to the housing crisis, is it a good plan to pump prime the economy? Or is it a prescription for another bubble? Some argue, correctly, that if you don't have good credit, lowering rates won't help (and if you don't have good credit, is making it easier for you to get a mortgage a good thing, or is it exactly what went wrong last time, at least partially?) Thoughts?