The winner of the Democratic presidential race between Barack Obama or Hillary Clinton will face the Republican they least wanted to meet in the general election.

John McCain’s imperfections for many conservatives make him a significantly more attractive candidate for voters who might otherwise have been tempted to back the Democrats.

Polls had consistently pointed to a landslide victory for both Mrs Clinton or Mr Obama against Mitt Romney but the RealClearPolitics.com average of recent surveys suggest that Mr McCain is locked in a statistical tie with both Democratic candidates.

While Mr McCain’s views on issues such as climate change and immigration reform put him at odds with Republican orthodoxy, the same maverick attitudes may yet secure crucial backing from Latino and independent voters in November.

He still has the considerable task of uniting his party behind him but he can now begin work knowing that his Democratic opponents are preparing to slug it out all the way to the presidential convention in August.

Yesterday he wasted little time in drawing a distinction with Mrs Clinton and Mr Obama, whom he accused by name of wanting to increase the size of government, raise taxes and withdraw from Iraq for “political expediency”.

Even before yesterday Mr McCain’s emergence as the Republican front-runner had caused Mrs Clinton and Mr Obama to make competing claims to a Democratic electorate craving victory over which of them was best placed to beat him.

On Tuesday night Mr Obama once again contrasted his ability to gain support from across the spectrum with the steadfast hostility towards Mrs Clinton from as much as half the electorate. He warned Democrats that they should not risk “going into this election with Republicans and independents already united against us”.

Although Mrs Clinton has enjoyed a good relationship with Mr McCain, even engaging in a vodka-drinking contest on a Senate trip to Estonia four years ago, she has begun raising the spectre of past Republican presidential campaigns that have mounted ferocious assaults on Democratic nominees. Mrs Clinton claims that, unlike Mr Obama, she has been through the test of fire over the past 16 years – “vetted” as she sometimes puts it – and that Democrats know she can stand up to the Republicans.

On Saturday Mark Penn, her chief strategist, issued a memo entitled “Hillary is the Democrat to Beat McCain”. He suggested that Mrs Clinton’s negatives were “fully factored in” whereas voters did not – yet – know enough about Mr Obama. “Once the Republican machine begins to methodically attack him, [OBAMA]will lose independent support,” he added.

Mrs Clinton often points to her greater foreign-policy expertise as a quality that she believes will be needed against Mr McCain, who has made national security a signature issue and strongly supported the “surge” of troops in Iraq last year.

In a recent debate, Mrs Clinton said: “I am better positioned and better able to take on John McCain . . . when it comes to issues about protecting and defending our country.”

Mr Obama shot back: “The way to win a debate with John McCain is not by nominating someone who agreed with him on voting for the war in Iraq.”

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