Shinzo Abe will almost certainly become the nation's longest-serving prime minister next month. Whether he will be remembered as a success could well hinge on how the economy weathers the consumption tax hike.

Legislation raising the tax to 10 percent from 8 percent took effect Tuesday, a long-planned step intended to help the government rein in the world's largest public debt load.

But it's a risky one — past tax hikes have tanked the economy and derailed political careers.