The easiest way to look at the battleground states, also known as swing states, is to go alphabetically. The first state that anyone predicts has a chance to be a battleground state is Arizona.
Here is a chart of the presidential election outcomes from 1976 through 2012:
With this chart, it looks like Arizona has been trending Democratic over the 1976 – 2012 time period. But there are four years that deserve notice: 1976, Carter followed 4 years after Nixon and people really wanted a change; 1980 and 1984 Reagan was a Republican superstar that pulled Republicans and Democrats; and 1988 Bush 41 promised to continue Reagan’s progress. Both the Republican and Democratic parties were different back then. In addition, the United States was still reeling from the Watergate scandal.
A better statistic to measure Arizona by would be 1992 – 2012:
As this chart shows, the trend in recent history has been toward the Republican party. The only time that Arizona has voted Democratic since 1992 has been Bill Clinton’s second term. While it is possible that Donald Trump’s attacks on John McCain as well as Arizona’s previous support for a Clinton will be enough to put this state back in play, it is going to take quite a bit of work.
As of right now — pending state level polling — I expect Arizona to go to the Republicans.