Leading article: Now the right has its own primary race to savour

In the opening weeks of this year's US presidential race, attention from outside America has focused, for obvious reasons, on the enthralling contest for the Democratic nomination. The Republican side has tended to be neglected. This should not be so from now on. Mitt Romney's convincing victory in the Michigan primary on Tuesday night has thrown the Republican race wide open. The three leading contenders have one victory each. They now go to South Carolina, and thence into the multiple contests of Super Tuesday, with all to play for in the battle for money and votes.

Mr Romney's victory – and John McCain's defeat – in Michigan can be explained in several ways. Mr Romney always had more funds at his disposal; without a win to his name, he was probably the more desperate. He also had the closer local connection, in that he was born in Detroit and his father was a well-regarded state governor. But his trump card was probably his concentration on the economy and his successful record as governor of Massachusetts. With rising unemployment, a flagging car industry and the rusting ruins of a heavy-industrial past, Michigan was ripe for Mr Romney's promises of generous help to mount an economic revival.

In his blunt warnings that many traditional jobs would not be coming back, Mr McCain was the most honest and realistic of the candidates. His remedies included more education and re-training schemes. But his nine-point defeat showed him to be clearly less in tune with voters. His relatively liberal stance on immigration, as well as his defence of the Iraq war, may also have been liabilities with different groups in a state which counts some of the highest concentrations of Arab-Americans in the United States. In all, Mr McCain could not repeat his victory of eight years before, when his straight-talking helped him to prevail over a callow George Bush.

Rudy Giuliani, the former Mayor of New York, may or may not be completely out of contention. But his gamble on remaining aloof until the big states hold their primaries appears to have backfired in a decisive way. With sixth place and only 3 per cent of the vote in Michigan, it will be very hard for him to catch up.

This essentially leaves three candidates in the Republican race, each with strong appeal to a different constituency. Mike Huckabee, a former governor of Arkansas, can be expected to have the white southern voters of the religious right in his pocket. John McCain's Vietnam war history still guarantees him the patriotic vote, and his gift for communication brings in younger voters and independents. But his long political experience is as a Senator, not as an administrator – which was Mr Romney's strongest suit in Michigan, where the economy became the central issue.

The lines of the Republican contest thus seem already set along policy distinctions, where the Democratic duel still hinges on personality. And so sharp are those distinctions that they could make it hard for Republican voters to unite around the victor, when the campaign proper gets under way. This hints at an early advantage for the Democrats, who are already more engaged than rank-and-file Republicans and more determined, after eight years of George Bush, to see one of their persuasion reclaim the White House.

Divisions among Republicans could also be a factor in tempting the current mayor of New York, Michael Bloomberg, to join the race as an independent. Such a late and plausible entrant could negate every earlier bet on the outcome in November. By keeping the Republican contest open, Michigan has probably made this more likely. But it has also had a more immediate effect: it has made the Republican contest overnight almost as compelling as that of the Democrats.