Leading article: The weakness exposed by Paul Ryan


Mitt Romney was yesterday formally nominated as the Republican presidential candidate, half-way through a campaign tour with his newly announced running mate. The warmth with which his choice of Paul Ryan, a fiscally conservative congressman, has been received by the party's rank and file, however, could have a double edge. It is not, after all, the Republican grassroots that Mr Romney has to convince before 6 November. It is the undecided middle and disappointed Obama-voters.

Plumping for Mr Ryan suggests Mr Romney felt the need to cement support on his party's right wing – a job he should have completed in winning the nomination. The custom is for candidates to lean to the extreme during the primaries, then move to the centre for the campaign proper. Mr Romney seems to be approaching his campaign the other way round.

The result, however, is an advantage of sorts for American voters. Mr Ryan's name on the ticket gives them a very clear choice between left and right. Mr Obama has a record to defend that is unusually liberal by US standards. He squeezed landmark healthcare reform through Congress and past the Supreme Court; he used public money to alleviate the worst effects of the financial crisis. He ended the war in Iraq, is in the process of ending the intervention in Afghanistan, and has shifted Middle East policy about as adroitly as was possible to accommodate the Arab Spring.

As the author of not dissimilar healthcare reform when Governor of Massachusetts, Mr Romney risked being seen as "soft" on this and other economic issues. With Mr Ryan at his side, there is no such danger – which conceals a liability of its own. Shrinking the state to the point where prized health provision for the elderly is trimmed – as Mr Ryan has proposed in the past – could lose Mr Romney otherwise safe Republican votes. Come September, the key for Mr Obama will be to decide which fights to pick. Defending the sanctity of the Medicare programme could be a good place to start.