Last year, the Pew Research Center released one of its occasional typological surveys of the US political landscape – the fifth in total, and the first since 2005. The findings of "Beyond Red v Blue" were significant in the context of the present presidential election – and, not least, Mitt Romney's pick of Paul Ryan as his would be vice-president. What it uncovered was a volatile politics in the midst of a period of transition, changing in ways that, perhaps, confounded some of the narratives that the media had assumed.

The political landscape, Pew assessed, had become more polarized and "doctrinaire at both ends of the political spectrum". That much, at least, is certain. At the same time, the survey observed, the space occupied by independents had expanded sharply since the last similar exercise, by some 7%. These are voters notable for holding strong views on individual issues while often defying old party orthodoxies and loyalties on others.

For those who identified themselves as "mostly Republican", the survey broke down the voters into two groups: "staunch conservative", characterised as "highly-engaged Tea Party supporters", and "Main Street Republicans", who together accounted for 20% of the general public. It calculated 37% were on the "mostly Democratic" side of the equation, which it broke down into three categories. Most interesting and perhaps most diverse, however, was the final group – "mostly Independent" – at 33% of potential voters (including Libertarians, described as "free-market, small government seculars"; "disaffecteds", who are defined as "downscale and cynical"; and "postmoderns", who are "moderates but liberal on social issues").

I think this survey explains some important things both about the Romney campaign, why he picked Ryan as his running-mate, and how that choice might play out.

It is a general truism of more recent democratic politics, as true in Europe as in the US, that successful campaigns do not tend to move sharply away from their own political centre – the point at which they can ensure both the support of their base while also, crucially, attracting voters from outside of that core group. Indeed, as David McKay has noted in his book American Politics and Society in his chapter on the Changing Role of Political Parties (see chapter 5, pdf):

"A defining characteristic of both the Democrats and the Republicans is that they have constantly sought to appeal to as wide a spectrum of voters as possible. As such, they have been obliged to promise general rather than specific benefits to voters."

McKay, too, noted the same emerging paradox in US politics as the Pew survey does:

"[W]hile the parties are more ideologically divided than they used to be, many voters remain generally apathetic and uninterested in politics."

If the present political environment is complex and toxic, characterised by a growing distrust of the political system, the present incarnation of Republicanism, the Pew survey argued, gifted at least some advantages – both in terms of its greater ideological homogeneity and in what it called an "intensity advantage" that delivered Tea Party gains in the 2010 midterms. Where it did identify an emerging Republican problem, however, was in "maintaining solid support among the GOP-oriented groups in the centre", not least among the "cross-pressured 'disaffecteds'" among the "mostly Independents", one of the groupings Romney needs to convince if he is to win.

Which brings us to the choice of Paul Ryan.

Faced with the challenges facing both Obama and Romney in persuading an electorate increasingly sceptical of both parties, one might have expected the Republican candidate to use his choice of vice-president to tick some boxes that would appeal outside of the core activist base. Indeed, only a few months ago, polling on Romney's vice-presidential pick – although hardly conclusive evidence of much – seemed to suggest that Ryan would not bring many advantages, compared with the likes of Marco Rubio, Jeb Bush or Chris Christie, to the Romney campaign, either in name recognition or in widening the ticket's appeal. So what, precisely, has Ryan brought to the party?

The reality, as Politico argued on Tuesday after off-the-record interviews with over a dozen anonymous GOP activists, is a whole bundle of new worries. For while Romney has assiduously avoided many specifics that might turn off key voters, Ryan is all about them. A dogwhistle ideologue, his positions on everything from his dogmatic pro-life voting record to his small government stance and his economic prescriptions that would cut taxes for the wealthiest and benefits for the poorest appeal most to "staunch conservatives" and Tea Party activists.

Confounding, too, is why Romney would have picked a running-mate whose views on an issue – his desire to reform the Medicare program – is likely to alarm strongly the group most over-represented even among "staunch conservatives": senior voters. As the Pew survey observed, older voters are represented "disproportionately" in the "staunch conservative" bloc where over 61% are 50 or older; yet, at least two polls have recently suggested that this same group (senior voters) is largely opposed to Medicare reform. This is doubly baffling as political strategy, as Nate Cohn argued in the New Republic earlier this week, because you would think Romney would not want to risk alienating seniors, who are the one significant group among whom Obama has not made gains between 2004-2008 and ought to be a natural Republican-leaning constituency.

But it is not just with seniors that Ryan brings risks to the Romney campaign. The Ryan Plan, his challenge to Obama's economic strategy which Romney has remarked flatteringly on and which has won broad backing from House Republicans, also seems out of step with the views of the wider electorate that Romney must win. For while "Beyond Red v Blue" noted that "majorities in most typology groups say the country will need both to cut spending and raise taxes to reduce the budget deficit", "staunch conservatives" alone remained the exception, saying the focus should be on cutting spending. Indeed, Ryan – most controversially of all – would actually cut taxes for the wealthiest Americans.

With the Republican presidential campaign already facing an escalating offensive over Ryan's views and how much Romney endorses them, it seems rather bizarre that the party's presumptive nominee – who lags behind the incumbent by most indicators – would pick as a running-mate a controversial figure with limited appeal, whose views he is now being forced to defend. The reality, as "Beyond Red v Blue" has described, and others have noted since Ryan's pick, is that Romney is caught on the horns of a dilemma. A candidate who is not "conservative enough" for his own base but needs to attract both wavering Democrats and Independents, he has failed to find an overarching and widely appealing political pitch that would allow him to hedge his bets.

Perhaps, in the present climate and configuration of the parties and where they stand, that was always impossible. But his choice – punting for Ryan to reassure the base – looks like poor politics and, potentially, an electorally fatal error.