PHOENIX, Arizona (AFP) — Senator John McCain appears set to romp home in Arizona's Republican primary, but only after tacking right and spending millions of dollars to counter a threat from a former conservative radio show host. Voters also head to the polls Tuesday for primary elections in Florida, Vermont and Alaska and results are being closely watched as a litmus test of the anti-incumbent mood in the run up to mid-term elections in November. Results such as Arizona may predict whether insurgent candidates, especially Republicans backed by staunchly anti-government Tea Party groups, will continue to make advances over those...