WASHINGTON • Senator John McCain is facing perhaps the toughest re-election bid of his long United States Senate career as he competes in an Arizona Republican primary overshadowed by party presidential nominee Donald Trump.
The former US Navy pilot, who turned 80 on Monday, is a leading member of the Republican establishment in Washington and was the party's 2008 presidential nominee.
His Republican challenger, Dr Kelli Ward, has attacked him as perhaps too old to live out his sixth term should he win. "I'm a doctor. The life expectancy of the American male is not 86. It's less," Dr Ward, a relatively youthful 47, told Politico recently.
A CNN poll released last week had Mr McCain ahead by 55 per cent to 29 per cent against Dr Ward in yesterday's primary, although a Gravis Marketing poll had Dr Ward in front by 45 per cent to 36 per cent.
Mr Trump, the ultimate anti-establishment presidential candidate, is proving to be a pivotal force in the primary. The Republican presidential nominee has endorsed Mr McCain and also Florida senator Marco Rubio in their re-election bids, even though he has rocky relations with both.
Mr Trump offended Mr McCain and many other Republicans last year by suggesting that the maverick senator was anything but a war hero because he was captured during the Vietnam War after his plane was shot down during a bombing mission.
In March, Mr Trump ended Mr Rubio's presidential bid by trouncing him in the Florida primary to cap a race in which the New York businessman taunted the first-term senator as "little Marco".
Mr Trump hesitated before ultimately endorsing Mr McCain for re-election earlier this month.
Dr Ward has expressed her allegiance to Mr Trump. She blasted Mr McCain, a member of the Senate's bipartisan "Gang of Eight" that drafted a comprehensive immigration reform plan in 2013 which has stalled in Congress, for helping to create an "immigration mess".
Mr Trump, who has called for the deportation of millions of illegal immigrants, is scheduled to deliver a major speech on immigration in Arizona today. The issue is vital to the state, which borders Mexico.
Mr McCain's likely Democratic foe in the general election, congresswoman Ann Kirkpatrick, has faulted him for endorsing Mr Trump.
In Florida, Mr Rubio was the clear Republican favourite in the Senate primary yesterday to win the opportunity to advance to the November election, where he faces a tougher race against likely Democratic opponent Patrick Murphy.
AGENCE FRANCE-PRESSE, REUTERS