For the first time in six years, the economy did not take first place in the annual Gallup poll on voter concerns. Instead, it's the first time that government leadership has topped the list, getting 18% in the survey.

But the poll also shows that there is not one, single overriding issue that troubles voters.

Sitting at just 18 percent, voter concerns over government leadership is the lowest figure for an issue at the top of the list in more than a decade, indicating that voter worry about a diverse group issues.

That’s in stark contrast to 2009, when 40 percent said the economy was their top concern, or 2007, when 33 percent said it was the War in Iraq.

“The lack of a single defining public issue could make candidates' task of honing a message for the election more complex,” Gallup analyst Lydia Saad wrote in her analysis of the poll.

With voter frustration aimed primarily at Capitol Hill, it could make life for incumbent lawmakers up for reelection very difficult.

Voters took out their frustration with President Obama in 2014 by sending a number of Democratic incumbents in Senate races packing. Republicans ultimately won a 54-46 majority in the upper chamber.

In 2016, with more than a third of U.S. senators up for reelection, it will be Republicans on the defense. Twenty-four of the 34 senators that are up for reelection next year are Republicans.

Gallup’s survey was based on interviews with more than 1,000 adults a month over the course of 2014 and has a margin of error 1 percentage point.

Immigration is a concern of  8% of the voters, but that number is probably going to go up once the battle is joined over Obama's executive orders. For Democrats, just 3% think that the gap between rich and poor is important -  a sure sign the issue is still a loser.

Bringing up the rear in the poll is national security at just 2%. With Islamic State on the loose and Putin throwing his weight around, that issue has the potential to become a lot more important in 2015.