Clinton comes out ahead, 39-34, with Libertarian Gary Johnson behind at 6 percent and Green Party candidate Jill Stein polling at 1 percent.
The Clinton campaign announced Monday that it will increase efforts in Arizona, including an additional $2 million in ad funding and sending First Lady Michelle Obama, Sen. Bernie Sanders (I-VT) and other speakers to the historically-red state.
The former secretary of state has expanded her lead in Arizona since the pollster last surveyed the state. In August, the poll showed Clinton +1 and now she leads +5 before the final presidential debate.
If Clinton's lead in Arizona polls proves accurate on Nov. 8, it will mark the first time the state preferred the Democratic presidential candidate since 1996.
The Arizona Republic/Morrison Institute/Cronkite News poll was conducted Oct. 10-15 via live telephone interview among 713 likely Arizona voters. The survey calculated margin of errors for each candidate's poll results, giving Clinton plus or minus 4.3 percent, Trump plus or minus 3.8 percent, Johnson plus or minus 1.6 percent and Stein plus or minus .4 percent.
TPM's PollTracker Average for the presidential election in Arizona shows a tossup, with Clinton leading Trump, 41.6 to 40.6.