Romney's plan? Wouldn't you like to know.

When Mitt Romney was governor of liberal Massachusetts, he supported abortion, gun control, tackling climate change and a requirement that everyone should buy health insurance, backed up with generous subsidies for those who could not afford it.

Now, as he prepares to fly to Tampa to accept the Republican Party's nomination for president on Thursday, he opposes all those things. A year ago he favored keeping income taxes at their current levels; now he wants to slash them for everybody, with the rate falling from 35 percent to 28 percent for the richest Americans.

All politicians flip-flop from time to time; but Romney could win an Olympic medal in it. And that is a pity, because there is much to like in the history of this uncharismatic but dogged man, from his obvious business acumen to the way he worked across the political aisle as governor to get health reform passed and the state budget deficit down.

The Economist shares many of his views about the excessive growth of regulation and of the state in general in America, and the effect that this has on investment, productivity and growth. After four years of soaring oratory and intermittent reforms, why not bring in a more businesslike figure who might start fixing the problems with America's finances?

But competence is worthless without direction and, frankly, character. Would that candidate Romney had indeed presented himself as a solid chief executive who got things done. Instead he has appeared as a fawning PR man, apparently willing to do or say just about anything to get elected. In some areas, notably social policy and foreign affairs, the result is that he is now committed to needlessly extreme or dangerous courses that he may not actually believe in but will find hard to drop.

In others, especially to do with the economy, the lack of details means that some attractive-sounding headline policies prove meaningless (and possibly dangerous) on closer inspection. Behind all this sits the worrying idea of a man who does not really know his own mind. America won't vote for that man. The convention offers Romney his best chance to say what he really believes.

There are some areas where Romney has shuffled to the right unnecessarily. In America's culture wars he has followed the Republican trend of adopting ever more socially conservative positions. He says he will appoint anti-abortion justices to the Supreme Court and back the existing federal Defense of Marriage Act (DOMA). This goes down well with Southern evangelicals, less so with independent voters: witness the furor over one (rapidly disowned) Republican's ludicrous remarks about abortion and "legitimate rape." But the powers of the federal government are limited in this area; DOMA has not stopped a few states introducing gay marriage and many more recognizing gay civil partnerships.

Even if it is unclear what would follow from that, risking a trade war with one of America's largest trading partners when the recovery is so sickly seems especially mindless. Some of his anti-immigration policies won't help, either. And his attempts to lure American Jews with near-racist talk about Arabs and belligerence against Iran could ill-serve the interests of his country (and, for that matter, Israel's).

Once again, it may be argued that this will not matter: previous presidents pandered to interest groups and embraced realpolitik in office. Besides, this election will be fought on the economy. This is where manager Romney should be at his strongest. But he has yet to convince: sometimes, again, being needlessly extremist, more often evasive and vague.

In theory, Romney has a detailed 59-point economic plan. In practice, it ignores virtually all the difficult or interesting questions (indeed, "The Romney Program for Economic Recovery, Growth and Jobs" is like "Fifty Shades of Grey" without the sex). Romney began by saying that he wanted to bring down the deficit; now he stresses lower tax rates. Both are admirable aims, but they could well be contradictory: so which is his primary objective? His running mate, Paul Ryan, thinks the Republicans can lower tax rates without losing tax revenues, by closing loopholes. Again, a simpler tax system is a good idea, but no politician has yet dared to tackle the main exemptions. Unless Romney specifies which boondoggles to ax, this looks meaningless and risky.

On the spending side, Romney is promising both to slim Leviathan and to boost defense spending dramatically. So what is he going to cut? How is he going to trim the huge entitlement programs? Which bits of Ryan's scheme does he agree with? It is a little odd that the No. 2 has a plan and his boss doesn't. And it is all very well promising to repeal President Obama's health care plan and the equally gargantuan Dodd-Frank act on financial regulation, but what exactly will Romney replace them with -- unless, of course, he thinks Wall Street was well-regulated before Lehman went bust?

Romney may calculate that it is best to keep quiet: the faltering economy will drive voters towards him. It is more likely, however, that his evasiveness will erode his main competitive advantage. A businessman without a credible plan to fix a problem stops being a credible businessman. So does a businessman who tells you one thing at breakfast and the opposite at supper.