The potential of Arizona becoming a swing state has been one of the big story lines of the 2016 presidential race -- with both campaigns focusing efforts here and recent polls showing it's a tossup.

Hillary Clinton’s campaign manager Robby Mook said Monday the campaign is putting $2 million toward ads in the state and first lady Michelle Obama, Chelsea Clinton and Sen. Bernie Sanders are all scheduled to make stops this week in Arizona.

Donald Trump has made six stops in Arizona along his campaign trail -- most recently in Prescott Valley, a town with one of the highest Republican turnouts in the state.

Whether Arizona's color changes or not, the state could have one of the biggest impacts on the race for president, according to a new study from WalletHub.

The study ranks Arizona as the No. 1 state for the most powerful voters in the upcoming presidential election.

“In a presidential election, voter power varies widely by state. While all votes are theoretically counted equally -- one person, one vote -- the choices of swing-state citizens are more influential,” the personal finance website wrote.

To determine the rankings of the states with the most and least influential voters, WalletHub calculated the “Voter Power Score” using the “win probabilities” from

They graded each state election on a 100-point scale, 100 points for states that have a 50 percent chance of swinging red or blue and 0 points to the states with no chance of determining the election.

They then multiplied the win probability score by the number of electors in a given state and divided the product by the state’s 18 and older population. The result was multiplied by 1,000,000 in order to calculate the final power score for that state.

[(Win Probability Score x Number of Electors) / Total Population Aged 18 & Older] x 1,000,000

Arizona was No. 1 with a Voter Power Score of 207.05, followed by Iowa (189.88) and Alaska (188.03).

California (0.37) has the least powerful voters in the upcoming presidential election, according to the study.

For the upcoming Senate election, Arizona ranks as No. 18 while New Hampshire has the most powerful voters.