Leading article: Small countries, big spenders

Much has been written about what the Liberal Democrats could do in a hung parliament, but Nick Clegg and his colleagues are not the only ones whose position could be greatly strengthened if, after 7 May, the Prime Minister has to barter for every vote in the House of Commons.

The death blow to the Labour government in the last hung Parliament, in 1979, was not dealt by the Conservatives or the Liberal Democrats. It was a vote of no confidence tabled by the Scottish nationalists, which passed by a majority of one. It is conceivable that this time the parliamentary arithmetic could again be so close that a government could survive or fall on the votes of the two nationalist parties, the SNP (led today by the wily and assured Alex Salmond) and Plaid Cymru.

Having these two parties exercising an influence on national politics could be a benefit. It is unlikely, for instance, that the UK would have gone to war in Iraq if the SNP and Plaid had had a decisive say in the past. We could avoid the wasteful expense of renewing Trident, or introducing ID cards, if they have a decisive say in the future. A minority Labour government dependent on SNP and Plaid support could turn out to be more radical than a majority Labour government ever dared to be.

But on the present showing, the more likely outcome is a minority Conservative government. It is hard to see what policies an administration led by David Cameron could offer that would motivate the nationalists to want to keep them in power. The Conservatives were the very last party to support devolution and are the least keen on further reforms that might undermine the unity of the United Kingdom. David Cameron advocates small government and a Big Society. The nationalists are big spenders. The SNP manifesto, unveiled yesterday in Glasgow, includes costly promises to maintain free personal care for the elderly in Scotland. They believe, bluntly, in big governments for small countries.

With so few big ideas to share, the temptation on both sides might be to settle for small gains, exchanging a few infrastructure projects and job creation schemes in Scotland and Wales for critical votes in the Commons. The Americans have a name for that sort of bartering. They call it pork barrel politics. It would be a shame if the SNP or Plaid Cymru lowered themselves into the pork barrel.