Sarah Palin and John McCain reunited on campaign trail

Sarah Palin was due to campaign with Senator John McCain on Fraiday, helping the man who launched her national political career to save his own.

The former Republican vice-presidential candidate and one-time Alaska governor has become a conservative star whose supporters hope will run against President Barack Obama for the White House in 2012.

But Mrs Palin is putting this aside to campaign for Mr McCain, her former running mate who is viewed with deep suspicion by many conservatives and faces a tough primary challenge in Arizona from Right-wing talk show host and former congressman JD Hayworth.

She was due to boost Mr McCain's conservative credentials at rallies in Tucson on Friday, and in the Phoenix suburb of Mesa on Saturday.

They were also due to hold a fundraising event on Friday at the same Phoenix hotel where they conceded the presidential election in November 2008 and Mrs Palin clashed with McCain aides, who refused to let her make a speech.

Mr Hayworth has tried to define himself as "the consistent conservative" in contrast to the "maverick" McCain who has worked with Democrats on issues such as reducing greenhouse gas emissions and restricting campaign donations.

The former congressman has used his radio show to lambast Mr McCain for working with the late Senator Edward Kennedy - a hate figure for many Right-wingers - on creating a pathway to citizenship for illegal immigrants - a hot-button issue in Arizona, which borders Mexico.

Putting a brave face on Mrs Palin's decision to hold three events for her former running-mate, he said: "We look forward to having Governor Palin's support following the primary. But we welcome her and we understand why she's in the state stumping for McCain."

Mrs Palin has vigorously criticised Mr McCain's top presidential campaign advisers, describing tensions with them and accusing them of trying to keep her "bottled up". But the former Alaska governor has avoided criticising Mr McCain himself.