By Steve Schifferes
BBC News
The Democrats have recaptured the middle ground in their electoral victory in the mid-term Congressional elections.
And for many, bread-and-butter issues like the economy and corruption were as important as Iraq.
Key swing groups of the electorate have returned to the Democrats, according to exit polls and opinion polls conducted shortly before the results were announced.
Even if the Democrats do not recapture the Senate, it is clear that the Republicans must do better among these swing voters if they are to retain the presidency in 2008.
The Democrats' success has been due in no small part to their ability to appeal to voters on issues that matter to them at home, and a perception that the Republican Congress has been ineffective and scandal-ridden.
Among the most important groups that have swung back towards the Democrats are married women - a key group that supported Mr Bush in 2004 - suburban voters, the elderly, and middle income voters.
Women voters
One of the most important factors in US voting is the "gender gap" - the tendency of Democrats to gain more votes among women.
In the past two elections however, while single women supported the Democrats, married women had moved towards the Republicans.
At this election, married women split 50%-49% to the Democrats, and women with children, and working mums, were 55% Democratic.
Women provided the margin of victory in the narrow Senate win for Claire McCaskill in Missouri, where stem cell research was an important issue.
Gains in the suburbs
Another key group was suburban voters, who represent nearly half the electorate, and where Republicans had been building up an advantage for some years.
Suburban voters broke 53% to 45% to the Democrats in this election according to exit polls, while the Democrats increased their advantage in large and small cities.
Many of the key Democratic gains in the House of Representatives were in suburban seats and small cities, ranging from the suburbs of Phoenix, Arizona (the 5th district), to Denver, Colorado (7th district) to Louisville, Kentucky (where longstanding Congresswomen Anne Northrup was defeated) to the suburbs of New York and Philadelphia.
Even in traditionally Republican rural seats, the Democrats were running neck-and-neck as a percentage of the overall vote.
Finally, this election represented a return of middle-income voters (making between $50,000 and $100,000) to the Democratic party.
The Democrats gained a 53% to 46% advantage with this group, which makes up nearly 40% of the electorate, and matched the Republicans with voters earning $100,000 to $150,000.
Economic issues played an important role in bringing middle and lower income voters back to the Democrats, especially in Midwestern states like Ohio, Indiana, Pennsylvania and Michigan, which have been hard-hit by an economic slowdown.
Polling data shows that many middle-income voters felt they did not benefit from economic growth in the last few years, and evidence suggests that there has been hardly any increase in real wages, despite the recent boom.
Key issues
Indeed, the exit polls suggest that the economy was seen as a 'very' or 'extremely' important issue by more voters than any other issue - and those voters went 60% to 38% for the Democrats.
And if this election was a referendum on George Bush and his conduct of the war, it is also clear from the polling data that disgust with Congress - and its corruption and sex scandals - was also an important factor.
The exit polls suggest that corruption was a very important issue to three-quarters of voters, which also broke strongly for the Democrats.
And the number who disapproved of how Congress was handling its job (62%) was higher than those who disapproved of how President Bush was handling his job (58%).
Those who thought Iraq was an extremely important issue also tended towards the Democrats.
There were only two issues - values (such as abortion) and immigration, where the Republicans had the advantage - but neither of these were as important to voters.
Religion and turnout
Another key factor in US elections has been the influence of religion on voting.
Evangelical or born-again Christian voters, who make up one-quarter of the electorate, broke strongly for the Republicans in this election - although by a reduced percentage compared with 2002.
Their turnout may have been reduced by the corruption and sex scandals among Republicans, and concern that the Congress had not delivered on much of the conservative value agenda.
But Catholics, who also make up a quarter of voters, returned strongly to the Democratic party, with a 56% to 43% advantage for the Democrats.
This may have helped Democrats win house seats in Arizona and New Mexico as well as Senate seats in the rust-belt states like Ohio and Pennsylvania, where pro-life Democratic challenger Bob Casey won a big victory over incumbent Rick Santorum.
Hispanics, black voters, and secular voters also became even more partisan for the Democrats, reversing the hopes of the Republicans, who had some success in recent elections in reducing the Democratic lead, especially among Hispanics.
If the Democrats can continue to mobilise their traditional base, and appeal to the key swing groups, they stand a good chance of reversing the Republican tide of the past decade.
But this election was relatively unusual, in the sense that national issues, such as Iraq, corruption, and the economy, rather than local issues or personalities, dominated the results.
In the next presidential election, values and personalities could well return to play a leading role in swaying the voters.