Immigration and higher taxes for the rich
Taxing the rich and cracking down on immigration are two policies which share common features. Both are overwhelmingly popular with the public in opinion polls. Yet Labour were unelectable when they called for higher taxes for the rich in the 1980s and 1990s, and the Tories were unelectable when they warned about Britain becoming a foreign country in 2001, and asked if we were thinking what they were thinking in 2005.
In both cases, the popularity of the individual policies were less important than the fact that they signalled something bad about the party - that Labour was hostile to success and aspiration, and that the Tories were full of xenophobic bigots.
Some commentators, like Danny Finkelstein for the Tories or David Aaronovitch for Labour, would argue that it is still the case that occupying the "centre ground" of British politics means steering clear of taxing the rich like Foot and Kinnock or banging on about immigration like Hague or Howard. They point to David Cameron's emphasis on 'detoxifying' the Tory 'brand', following in the footsteps of Tony Blair and New Labour.
I think that in fact the centre ground has shifted, particularly since 2007, and that Labour and the Tories have in practice agreed a new and more populist consensus which is much tougher on immigration and in favour of higher taxes on the rich.
And then there is our old friend Tom Harris MP. On immigration, he argues that "Immigration concerns must be heard, whatever the elite may say"; whereas on higher taxes for the rich he argues that, "No party that is seen to sneer at wealth, or which is suspected, because of its language, of treating the wealthy and the wealth creators as the enemy, can hope to win the confidence of the electorate."
In other words, Labour should adopt populist policies which have lost elections for right-wing parties in the recent past, but should shun populist policies which have lost elections for left-wing parties in the less recent past.
This is an analysis which is less "we need to remain in the electable centre ground of British politics" and more based on the principle of "if those no good libruls are for it, I'm agin' it".