In the end, John McCain won handsomely. But another sitting Republican Senator was facing defeat yesterday after another round of US primaries underlining the dangers facing incumbents in November's mid-term congressional elections.
According to near-final figures, Mr McCain, his party's unsuccessful 2008 Presidential nominee, crushed his ultra-conservative opponent JD Hayworth by a 56-32 margin in Arizona.
But the victory came at a high price — $21m — and an enforced shift to the right.
Nonetheless Mr McCain can now look forward to victory in November's general election. The same cannot be said for Republican incumbent Lisa Murkowski in Alaska, who was trailing Joe Miller, backed by Sarah Palin and the insurgent Tea Party movement, by 48 to 51%, with only absentee votes still to be counted.
A Murkowski defeat would be a notable upset.
It would also be the biggest success yet in this election season for Ms Palin, who has been dispensing endorsements on conservative candidates who meet her approval.
Elsewhere, in the battle for the Republican gubernatorial nomination in Florida, former health care executive Rick Scott defeated the state's Attorney General Bill McCollum.
And Democrat Kendrick Meek beat a campaign by billionaire Jeff Greene in the primary for the state's vacant Senate seat.