It is hypothesis week on Capitol Hill. Yesterday, Paul Ryan, the House budget chairman, published a Republican plan he claims would restore the US deficit to balance within a decade. Today, Senate Democrats will offer their own plan to put the US on a fiscally sustainable course. Both have merits – although Mr Ryan’s is based on some unrealistic assumptions. But since neither stands a chance of being enacted, they are chiefly an exercise in showmanship. It is time for President Barack Obama to inject some ambition into the sterile US fiscal debate. There is still scope for him to go for a grand bargain in 2013.

There are two compelling reasons for Mr Obama to seize the initiative. The first is tactical. Aiming for a big fiscal overhaul based on lifting US competitiveness would help break today’s dismal tactical impasse. Most people had assumed the $85bn sequestration that Congress allowed to come into effect on March 1 would only survive a few weeks. Now it is likely to be wrapped into the resolutions that Congress will have to pass by March 27 to prevent a government shutdown.

There may be tweaks to allow agencies more scope over how the sequestration cuts are applied. These will only start to be felt in April. But the decision to shave up to 0.6 percentage points off this year’s US growth looks likely to stay.