Mitt Romney's strong record as a former Governor of Massachusetts made him the obvious choice as the Republican presidential candidate. His strength, after all, lies in economic management, the area where President Barack Obama is under most pressure, not least because of a stubbornly high 8.3 per cent unemployment rate.
But Mr Romney also has weaknesses, notably a lack of charisma or an appeal to conservative and evangelical Republicans.
These shortcomings see him trailing the President in opinion polls. Something had to change if his challenge was not to rely in large measure on a sudden deterioration of the American economy. This has been supplied by his selection of free market Congressman Paul Ryan as his vice-presidential running mate.
Mr Ryan's youth and zeal have re-energised the Republican campaign. Even the uninspiring Mr Romney appears rejuvenated. It has become quickly apparent that he has avoided the Republicans' blunder in the last presidential race, when John McCain ran with the inexperienced Sarah Palin.
The 42-year-old Mr Ryan, who chairs the House budget committee and has spent half his life in Washington, is no political tyro. Yet his selection, as with that of Ms Palin, says much about Republican frailties and could yet prove as problematic.
In the normal course of events, candidates tend towards extreme policies during primary campaigns. When they win their party's nomination, they move towards the centre where the majority of the national vote lies.
In picking Mr Ryan, the moderate Mr Romney has moved in the opposite direction. He is employing Mr Ryan's small-government ideology to ensure that he wins the vote of Republicans allied to the strident and partisan Tea Party movement.
That is an odd approach, not least because Mr Romney should have already sewn up this arch-conservative vote. But he obviously still fears that group's strong dislike of President Obama could translate into a non-vote, rather than automatic support for him.
And by cosying up to them through Mr Ryan, he risks alienating the undecided middle ground and the many disappointed people who voted for President Obama. The Wisconsin Congressman is, after all, best known for his advocacy of deep cuts in social spending to bring United States debt and deficits under control.
Mr Ryan will relish the chance to pitch his message of fiscal responsibility, balanced budgets and deficit reduction to the American people. But his proposed budget, which was unsurprisingly rejected by the Democrat-controlled Senate, would have, among other things, slashed public spending on the President's Medicare programme. That will be a hard message to sell to many elderly people, including those notable for their numbers in the key state of Florida.
And while Mr Romney lauds US success in space, most recently with the Curiosity mission to Mars, Mr Ryan would probably also consider that non-crucial spending. Again, thousands of people in Florida are employed on the space programme. The nation's farmers will, likewise, be eyeing subsidies nervously. Democrats have been quick to reinforce such points. And to emphasise that Mr Ryan's selection presents Americans with clear policy choices.
Mr Romney's moderate approach has been transformed overnight into a radical prescription. That provides plentiful ammunition for the Democrats.
The danger for them is that any worsening of the country's economic woes before the November 7 election would encourage Americans to think more positively of the Republican prescription. Extreme policies find a resonance in extreme times. At this point, President Obama remains a clear favourite. But Mr Romney has gambled in a way that could yet pay the ultimate dividend.