Voter turnout is a critical issue in the United States because the majority of Americans do not vote. Elections are critical to a nations vitality and this can be seen in other countries where rebel groups rise, and massive people flock to elections to be heard on where they want the direction of the country to go.
I believe that it likely is, because people are not stupid. Americans are starting to realize one simple fact, that all politicians are the exact same person. If every person is the exact same, why even waste your time that morning going to vote? I know I certainly do not because I know that no matter what it will just be more of the same.
I think voter turnout trends up and down depending on how hyped the public is about the candidates in an election, if both canididates are getting a lukewarm reception then the turnout will be lower but if one of the candidates is exciting and can inspire people then people will turnout to vote for him or her, so overall I wouldn't say voter turnout is declining.
Actually, voter turnout has increased in America within the last couple of elections. There was a time where it had been declining, but after several campaigns of people trying to get the vote out, there was a marked improvement. Especially within the minority community and the democratic voters. Hopefully this trend continues.