The rising poll numbers come after a strong performance in Wednesday's debate.
Retired neurosurgeon Ben Carson follows Trump in second place in the Grand Canyon State.
Trump's net favorables are up 16 percentage points in the last two weeks; Bush is down 6.
Another poll found Sanders pulling within 7 points of Clinton.
His lead over the Republican primary field is growing.
Forty-five percent said they consider her use of a private email server a "serious scandal."
Forty-nine percent of all voters also believe Trump will be the nominee.
A Republican hasn’t won the state in a presidential election since 1984.
PPP poll finds eight Republicans beating her in head-to-head contests in the swing state.
A majority also think the private email server endangered national security.