The charts were made from information contained in a recent Gallup Poll -- conducted between August 7th and 10th of a random national sample of 1,032 adults, with a 4 point margin of error.
Normally in an election year the most important issues are economic issues -- especially when the economy is faltering and unemployment is high. But 2014 is a bit different. The people are concerned about the economy and unemployment, but they have seen Congress squabble for years now -- refusing to compromise and take action to fix either of those problems. And that has made them very angry and disgusted at the Washington politicians -- and that anger is showing up as the issue most consider important in this election.
There is a strong belief among the public that nothing will be done to solve the nation's real problems until something is done about the current politicians in Washington -- and that has resulted in a definite anti-incumbent mood among voters this year. And with the presidency not being voted on until 2016, and only a third of the Senate seats being contested, that anger is primarily being directed at the House of Representatives (where all 435 seats are up for election).
Representatives in competitive districts should be very afraid, regardless of party. But I think the Republicans should be afraid the most -- because they hold the current majority (and similar voter anger in the past has resulted in control of the House being flipped), and other polls have shown they have less support that the Democrats have.
The bottom chart shows this issue of anger with the politicians has been one of the main (if not the main) issues all year long. I doubt this will change before the November election.