Paul Ryan, Mitt Romney's chosen Vice-Presidential candidate, has a reputation for being the brains of the Congressional Republican Party. But while he talks the talk, his brains are seemingly used more for misleading the public than coming up with credible fiscal policy.

This reputation stems largely from his role at the head of the House of Representatives' budget committee, where Ryan has spent the last 18 months rejecting the Democratic budget, while presenting his own vision of how the Government should be funded, through the "Ryan Plan".

Ryan's alternative budgets were presented annually from 2008, when the Democrats took control of both houses and the Presidency, but the first one to be passed by the House was his 2011 plan, which made it to the Senate before being shot down 57-40. The plan was updated and reintroduced earlier this year, but again fell in the face of Democratic opposition once it made it through the House of Representatives.

The ideological heart of the Ryan Plan can be found in its fourteenth slide:

There's a lot wrong with this graph: it assumes that the American healthcare paradigm, a system which all parties recognise as broken, will continue unless Ryan steps in and changes the country to the "path to prosperity"; it attempts to predict the Federal fiscal situation in 2080 when we can't even reliably predict what it will be like in 2018; and it took a lot of cajoling to get the CBO (an independent financial analysis organisation, and the model for our own OBR) to actually accept that Ryan's plan would result in anything like the debt dynamics he suggests. But it serves one purpose admirably, which is to convince the American public that Paul Ryan is a man who is Serious About Debt.

Unfortunately, that's just not particularly true. As Wonkblog reminds us, looking through his voting history reveals a typical Republican pattern: concerned about high taxes and "handouts", but little fear of the deficit per se. Ezra Klein writes:

He voted for the George W. Bush tax cuts, as well as the war in Iraq and the unfunded Medicare Prescription Drug Benefit. Perhaps his most ambitious policy proposal prior to his celebrated budgets was the Social Security Personal Savings Guarantee and Prosperity Act of 2005, a plan to privatize Social Security. The program’s actuaries found that Ryan’s plan would require $2.4 trillion in additional costs over the first 10 years, and the Bush administration ultimately dismissed it as “irresponsible.”

And one doesn't really need to look into the distant past to learn that the deficit itself ranks rather low on Ryan's list of priorities. His budget plans, like most, are easily split into two sections: changes to taxation, and changes to spending.

The tax changes are relatively simple, clearly specified, and hugely regressive. Ryan has proposed cutting federal income tax rates down to a baseline of 10 per cent and a 25 per cent marginal rate for higher earners, down from the current maximum of 35 per cent, and offset those cuts by removing most tax credits used by the poorest. The end result is a massive transfer of the burden of taxation from the wealthiest to the worst off in society, noteably leaving Romney himself paying just 0.82 per cent of his income in tax:

But while Ryan's tax plan is specified rather precisely, his spending plan isn't. It is famous for the slash-and-burn approach it takes to Medicare (health insurance for the elderly), Medicaid (health insurance for the poor) and Social Security (pensions): Ryan proposes cutting the budget for the first by around a quarter, for the second by around three-quarters, and capping the cost of the second in the face of a rapidly ageing population.

These policies would greatly increase human suffering across America, and have been blasted as "simultaneously ridiculous and heartless" by the likes of Paul Krugman. But they fit the idea of a hardcore deficit hawk. What doesn't is Ryan's policies on everything else – literally. The plan lumps "everything else" (that's defence, infrastructure, education, the environment, the civil service, the FBI. . .) together into a category on which Ryan claims spending will be cut to just 3.75 per cent of GDP.

That's a stupidly low number. It's even lower in the context of Romney's promise to spend 4 per cent of GDP on defence alone; that defence has never cost less than 3 per cent; and that even Ryan calls for a short term increase in defence spending.

Simply put, there is no way that a Romney/Ryan government would ever be able to achieve its spending ambitions. It would try, and hurt millions of people in the process, but even while cuts which are "beyond draconian" are being put in place, it would fail.

So Ryan has a clear, politically easy and well specified plan to cut revenue, and a vague, politically impossible plan to cut spending. It doesn't take a prophet to see that the former would be achieved in six months, while the latter would likely never come close to fruition. The hole in the budget would easily exceed the worst excesses of the Bush years (and that's assuming the Romney/Ryan administration doesn't launch a war with Iran).

So Ryan can credibly claim to be the candidate of lower taxes (for the rich) and can probably claim to be the candidate of smaller government (just not as small as he promises). But the candidate of a lower deficit, the candidate who can fulfil the promise made in the chart at the top of this post, is not him.