THE Northern League has long been decisive in Silvio Berlusconi’s political career. When in 1994 the party withdrew its support from his first government, he lost power. It was not until after the League’s founder, Umberto Bossi, teamed up with Mr Berlusconi again in 2000 that he was able to regain it.So the media proprietor-turned-conservative politician was understandably jubilant when he revealed on January 7th that he had wooed the League’s leaders back into an alliance they deserted after the fall of his latest government in November 2011. Recent opinion polls have given the League, which wants greater autonomy for the north and tighter immigration controls, less than 6% of the national vote. Yet it remains crucial to the prospects of the Italian right in the general election scheduled for February 24th and 25th.The electoral rules, framed eight years ago by a minister from the League, tip the scales in the race for the Senate towards parties with a geographically concentrated following. The centre-left Democratic Party (PD) is currently well ahead in the polls. But a partnership between the League…