The electorate had 2 choices only.
They could vote for those that represented the party that started the war based on spin, the party that held power in both Senate and House and that had an almost continuous drip drip of disgraced and corrupt officials in elected office as wellas a party that continuously advocated continuance of a deeply unpopular war.
OR
A party that spoke against that war that denigrated those in power who were seen as corrupted both finacially as well as sexually.
When you have these two possibilities, you vote your perception as to who is the better able to run the country OR you vote against those that you consider to have spun against your interests.
In the US we have whether we like it or not, basically a two party system, so when one party is seen as being unfit to serve the electorate, that electorate has two choices,
1) Abstain from voting at all.
2) Vote for the opposition party.
By abstaining from voting you are in effect abrogating your rights and responsibilities as a citizen.
By voting for the opposition you are voting for someone you hope will correct the sins of those that were formerly in power.
With this last supposition, your hopes may well turn out to be incorrect, but until a more than 2 party system emerges in the US the only choices are those I have mentioned above.
I doubt that the democrats want the US to fail in Iraq, but I do believe they are deeply concerned by what was started and is seen as a war that was not necessary, no WMDs, no Terrorists other than those that arrived after the war was initially won, a steady drip drip of American bodies being returned to the US without any apparent improvement for the Iraqi population, and a continuance of what has esentially become a worsening civil war that the US and Allies are incapable of quelling.
This is I believe why folk voted democrat.
I am actually in favour of the so called "Surge" of troops to Iraq, but only on ONE condition, namely that the Iraqi Government take their responsibility for the ending of this civil war seriously.
If the Iraqi Gov. is incapable of doing this then the only solution for the US would be to pull out.
Another possibility would be to encourage the Kurds with their claim of the right to their own Territory which is currently in parts of Iraq/Syria/Iran. as well as Turkey.
What was originally seen by them as being Kurdistan, by encouraging them to at least reclaim those parts of that country currently within the borders of Iran and Syria, would I believe take an enormous amount of Syrian and Iranian attention away from Iraq.
Natuarally it would probably be the cause of anther conflagration in the Mid East.
But it would also almost certainly cause Iran and Syria to sit up and take notice, it would also cause the Maliki Gov. to take a step back and start thinking, what would happen if Kurdistan became an actuality, most of Iraqi oil is in Kurd held Territory.
Incidentally the Kurds are by and large not of either Sunni or Shi ite sects of Islam.