Leading article: A Republican echo chamber

The announcement that Sarah Palin, the Republican 2008 vice-presidential nominee, is joining Fox News as a commentator offers further proof of the fusion in America of politics and the media/entertainment complex. The phenomenon is nothing new – think merely of a former Hollywood actor named Ronald Reagan – but it has notably grown in recent years.

Fox in particular has become a home for out-of-power Republicans. Mike Huckabee, John McCain's closest challenger in the 2008 Republican primaries, as well as Newt Gingrich, the former House speaker, are among other political luminaries on its payroll. On the Democratic side, the former comedian Al Franken was a host on the liberal Air America radio network before winning a seat in the Senate. The advantages for Ms Palin are obvious. Regular appearances on the most watched cable news network in the US will give her an unmatched platform from which to launch, should she wish, a presidential campaign of her own in 2012.

Right now, her ambitions are unclear. Ms Palin is a divisive figure whom some moderate Republicans find hard to stomach. Her next high-profile public appearance will be at the inaugural national convention of the far-right and increasingly influential Tea Party protest movement next month in Nashville. But a pundit's chair on Fox will do nothing to diminish her present status as the most recognisable Republican in the land.

The benefits for the American political system on the other hand are less obvious. Fiercely competitive, with hours of empty air time to fill and desperate to win ratings, cable TV news and talk radio have coarsened politics. They have hastened the advent of the never-ending campaign, and have reinforced the polarisation that makes vital legislation so hard to enact – witness the warfare over health care reform.

By joining Fox, Palin will further seal herself in the conservative echo chamber that, for a while after the party's crushing 2008 defeat, made Rush Limbaugh, the bombastic conservative radio host, indubitably the most influential Republican in the land. Arguably, he still is. That is terrific for Mr Limbaugh's ratings. But it's not good for American politics.