Several key issues are likely to influence the way undecided voters turn in the US mid-term elections on 7 November.
Here, we look at what could play big in the Democrats' efforts to wrest control of the House of Representatives and Senate from the Republicans.
WAR IN IRAQ
Opinion polls this summer suggested more than half of Americans were pessimistic about US strategy in Iraq, with concern focused on rising death tolls and the war's indefinite duration.
Many Republicans fear the issue could affect their party's standing in the mid-terms. Some have joined Democrat calls for an immediate withdrawal.
The release of parts of a US intelligence report suggesting that America's involvement in the Iraq conflict has fuelled global terrorism is unlikely to reassure Republicans.
However, the White House has stressed elements in the report that conclude victory in Iraq would be a big blow to the enemy in the "war on terror".
President George W Bush has recently repeated a promise that the US will not leave Iraq until victory is achieved.
The Iraq issue may already have claimed one scalp: Senator Joe Lieberman's support for the Iraq war was a big factor in his defeat in a Democratic Party primary by anti-war challenger Ned Lamont.
President Bush has launched a vigorous defence of his security strategy ahead of the mid-term elections - and used it to attack the opposition.
In an unexpectedly political address on the fifth anniversary of the 9/11 attacks, he urged Americans to unite behind what he described as "the decisive ideological struggle of the 21st Century" - in his opinion, the "war on terror" against Islamist "fascists".
The approval by Congress of a controversial bill setting rules for the questioning and trial of foreign terror suspects is being seen as a political victory for the Republicans.
Although Mr Bush had to compromise to overcome a rebellion within his own party, he achieved most of what he wanted and will use the issue to accuse the Democrats of being soft on terror.
The legislation was opposed by Democrats, who argued it would deny terror suspects fundamental legal rights.
The House of Representatives has passed a bill that would grant legal status to the Bush administration's warrantless wiretapping programme - ruled unconstitutional by a judge in August - but the Senate has been unable to reach agreement on the legislation.
The Democrats are hoping to capitalise on concerns over the state of the US economy, which may be slowing down after a long period of growth.
Falling petrol prices will ease money worries for some voters
The biggest popular concern has been high petrol prices, which reached $3 (£1.60) per gallon on the back of rising oil prices this summer before falling back.
Another worry has been the state of the housing market, which looks like going into reverse after a huge boom in house prices in major cities, especially on the coasts.
The uncertainty about the state of the housing market and inflation has led the US central bank, the Federal Reserve, to pause after raising interest rates 16 times.
But the higher rates have not yet filtered through to consumers, many of whom have borrowed heavily against the value of their home.
In the longer term, there are bigger problems facing the US economy.
The strong growth in the past few years, fuelled by tax cuts, has led to a big increase in imports and a huge trade deficit with the rest of the world.
And the row continues over whether the tax cuts, which have mainly benefited the better-off, have helped economic growth and should be made permanent.
One reason why the average American does not feel better off is that real wages have barely risen over the past five years, with a growing inequality of incomes.
And although unemployment is down, it has not fallen as fast as in previous recoveries.
Some Democrats blame unfair foreign competition, especially from China, for exacerbating these trends.
The thorny issue of illegal immigration dominated political debate earlier this year, with emotions running high on all sides.
There is a general feeling that the US immigration system is failing but opinions differ widely, even within Republican and Democrat camps, on how to make it work.
Hundreds of thousands of people - many of them Hispanic - have marched in California and elsewhere to protest against plans to criminalise undocumented workers and to call for recognition of immigrants' contribution.
At the same time, anti-immigration groups have been patrolling US borders and confronting illegal workers in cities around the country.
Debate continues on how to reconcile contrasting immigration bills passed by the House of Representatives and Senate.
Both seek to tighten border security, but while the Senate bill includes a guest-worker programme and offers illegal immigrants a "path to citizenship" - ideas backed by Mr Bush - the House's "enforcement-only" bill seeks to deport illegal immigrants and make it a felony to remain in the US illegally.
The issue is politically awkward for the Republican party because it brings into conflict two of its core constituencies - social conservatives and the business lobby, who argue that immigrants provide much-needed labour.
Many Democrats, especially in states where immigration is a hot topic, have been taking a tough stance. Both parties must bear in mind the risk of alienating the Hispanic vote if they appear too strongly anti-immigration.
Another undeniable factor ahead of the mid-terms is the popularity - or not - of President George W Bush, even though his name appears on no ballot.
George Bush's personal approval ratings are low but rising
For months, the president's approval ratings have been low, buffeted by public disillusion over the Iraq war and concerns over rising energy prices. Criticism of his administration over Hurricane Katrina and a series of domestic political scandals have not helped.
However, more recent polls, some conducted since Mr Bush launched his political offensive on the war in Iraq and security in September, show a modest rise.
Some observers suggest Mr Bush's standing with the voters may have been helped by a drop in fuel prices.
Polls suggest there has also been a climb in the president's approval rating among Republicans - welcome news for candidates eager to ensure their supporters turn out to vote.
All sides will be watching the figures closely, since history shows that the governing party often suffers big losses in congressional elections even when the president is popular. This holds especially true in a second presidential term.
The actions of disgraced Republican ex-Congressman Mark Foley, who sent lurid e-mails to teenage boys, are dominating political discussion in Washington.
The top Republican in the House of Representatives, Dennis Hastert, is also under scrutiny, amid allegations his office covered up the scandal.
It remains to be seen whether a series of corruption scandals which have dogged the Republicans will hurt them at the polls.
Democrats have sought to portray figures like disgraced lobbyist Jack Abramoff and former House Majority leader Tom DeLay as the faces of a "culture of corruption" within the ranks of their political opponents.
Yet analysts say the scandal is unlikely to influence results across the country.
Congressional elections tend to pivot on local issues. So, while polls suggest just a quarter of Americans trust Congress as a institution, a large majority have faith in their own elected officials.
Nevertheless, there are a clutch of key races where corruption is very much a live issue.
In Montana - crucial to Democrats' hopes of winning control of the Senate - incumbent Republican Conrad Burns has been hit by claims that Abramoff had close ties with his office.
And there are fears the lingering taint of corruption may affect Republicans running for seats abandoned by figures like Mr DeLay or Ohio's Robert Ney.
One early casualty of the "Abramoff effect" was former US Christian Coalition head Ralph Reed, who lost the race for the Republican nomination for Georgia's lieutenant-governor.
The escalating costs of health care figured high on the list of voter concerns in polls earlier this year.
Over the past five years, the number of US citizens without health insurance has grown from about 40 million to about 46 million.
Meanwhile, tens of millions more have very real concerns about their employers' ability or willingness to continue paying their health costs.
Mr Bush has proposed a more portable health insurance scheme and tax-friendly health savings accounts.
His other big health initiative, the Medicare Prescription Drug bill, suffered some serious teething problems as it came into effect.
The Democrats will hope to gain ground with swing voters who are feeling the pinch of low wage growth and think a new administration might do more to bring down health care costs.
The Washington Post newspaper predicts those it terms "mortgage moms" - that is, "voters whose sense of well-being is freighted with anxiety about their families' financial squeeze" - may well play a big role in deciding the mid-term results.
As ever, both Republican and Democratic Parties will seek to capitalise on social and ideological differences to mobilise their respective supporters.
The legislatures of a number of states have attached ballot initiatives to the vote for House and Senate candidates, in a bid to bring to the polls electors who might otherwise have stayed at home.
As in 2004, proposals to ban same-sex marriage are being used to appeal to religious conservatives. Voters in six states - Idaho, South Carolina, South Dakota, Tennessee, Virginia and Wisconsin - will be balloted on the issue.
The abortion debate may also galvanise South Dakota, where the legislature passed a law banning almost all abortions in March this year. Pro-choice campaigners collected enough signatures to put a referendum on the ballot, giving voters the option to repeal the ban - or back it.
Meanwhile, in Missouri, Democrats are hoping that ballot measures to finance embryonic stem cell research and increase the minimum wage will play in favour of their Senate candidate.
But Republicans could benefit if conservatives and anti-abortion groups come out to oppose the stem cell initiative.
Smoking bans or higher tobacco taxes are on the ballot for California, Florida, Nevada, Idaho and South Dakota; an initiative on tax-limitation measures will be put to voters in Florida, Maine and Rhode Island.
Meanwhile the issue of eminent domain - or the government's right to take private property for public use - is a ballot initiative in several states. Its inclusion is in part a response to a controversial Supreme Court ruling last year.