The battle for the White House will be fought in the centre

Al Gore has made a small but calculated gamble by choosing Joseph Lieberman, the highly respected senator from Connecticut, as his running-mate in what is is now plainly an uphill battle to retain Democratic control of the White House in the election on 7 November.

Al Gore has made a small but calculated gamble by choosing Joseph Lieberman, the highly respected senator from Connecticut, as his running-mate in what is is now plainly an uphill battle to retain Democratic control of the White House in the election on 7 November.

Mr Lieberman is an Orthodox Jew, the first to run on a major national ticket, and Mr Gore's reckoning is that his country is ready for such an innovation. It may seem odd there is any doubt in the matter, given the prominence of Jews in almost every walk of American life, and the rock-solid alliance between the US and Israel. But the unwritten conventions of US politics have always lagged behind the realities of national life. Most probably Mr Lieberman's faith will be low on the list of factors by which his countrymen judge him.

Two factors above all appear to underpin his selection. Mr Lieberman is the incarnation of high moral standards in public life. He was the first and most outspoken Democratic critic in the Senate of Bill Clinton's conduct in the Monica Lewinsky scandal; there could be no more visible pledge that a Gore White House will operate on a higher moral plane. Given the ethical questions over fundraising that still dog the Vice President, that assurance is not superfluous.

Second, Mr Lieberman will have considerable appeal for moderate Republicans, and especially to independents - an increasingly important category of voter which, ominously for Mr Gore, has been leaning in the direction of his opponent, George W Bush. He comes from one of America's richest, most business-oriented states, has a hawkish foreign policy record and has been a staunch supporter of the military - including the $2bn-a-copy Seawolf submarine project, built, by no coincidence, on his own Connecticut turf.

The doubt, of course, is whether Mr Lieberman can help to provide that jolt of political electricity that the limp Gore campaign so desperately needs as it heads for the Los Angeles convention. He is solid, experienced and highly competent, but, his religion apart, offers little novelty. His choice is a further sign that campaign 2000 will be fought in the centre. As for the vice-presidential debate with the Republicans' no less august Dick Cheney, it may give worthiness a whole new name.