Why did the Democrats take over Congress, and does it portend a larger and long-lasting Democratic majority?

To get at these answers we have to try and understand why Democrats picked up six Senate seats, 29 House seats and 53 percent of the total House vote, their largest share of the vote since 1986.

Democrats deserve credit for running a very disciplined campaign and, most importantly, for recognizing that the extremely negative political environment for Republicans this year meant all they had to do was present themselves as a tolerable alternative. But the real answer to this election is found not in what the Democrats did but why the Republican majority crumbled.

First, three broad policy issues hurt Republicans on the margins:

1) Spending: Ironically, the good economy eliminated any excuse for the dereliction of Republican government on spending. Many voters were simply fed up with watching their money go to outrageous earmarks and bridges to nowhere, all courtesy of a Republican Congress and a President who were supposed to stand for fiscal restraint.

2) Schiavo and Stem Cells: Fairly or unfairly, the perception that religious beliefs were trumping individual family choices, science and medical research hurt Republicans with moderates, independents and libertarian-leaning conservatives.

3) Immigration: The immigration debate hurt Republicans both ways as frustration with the inability to secure the border added to a lack of faith in Republican government, and the loud and angry rhetoric over "amnesty" turned off Hispanics and voters in the middle.

Going along with these policy issues was the backdrop of sleaze and scandal symbolized by the entire Jack Abramoff affair. The carefully-timed Mark Foley scandal reinserted this issue at a critical time in the campaign which further alienated moderate and independent voters. This is quite evident by the congressional ballot polls which showed a clear five-six point boost for the Democrats in the generic ballot following the Foley eruption.

On scandal alone the Republicans lost one Senate seat (Montana) and six House seats (Ohio-18, Pa.-10, N.Y.-20, Texas-22, Fla.-16, Calif.-11). Every one of these places voted for George W. Bush by eight or more points two years ago.

But make no mistake about it: the driving issue in this election was Iraq. Heading into Election Day the big unknown was how the public would speak on the issue of the war. It was clear before the election that there was a growing realization in the country that Iraq was not going well, that it was a mess and a significant problem. However, it was unclear whether that frustration would be enough of a catalyst to get the voters who chose to go to the polls to side with the Democrats over the Republicans. The answer is clear that it was.

The vote last Tuesday was not necessarily a vote for a Murtha-style withdrawal, but it was a clear and unambiguous vote against the status quo policy in Iraq and President Bush's leadership on Iraq in particular. The public recognized that a vote for a Republican Congress would in fact be a de facto vote for a continuation of the current Iraq policy. In simplest form, then, the midterm election was a vote of no-confidence by the country on the Bush administration's Iraq course of action.

That is the reason Democratic gains are potentially far softer and less far reaching than many Republican or Democratic partisans appreciate. This election was not a vote in favor of Democrats, nor was it a blanket repudiation of the Iraq war as some on the left have mistakenly assumed. The only consensus in the country is the "stay the course" policy in Iraq had to change, but the shape that change takes moving forward is where it will start to get very tricky for Democrats.

With control of Congress, Democrats will no longer be able to pass the buck on where they truly stand on Iraq. And for all the talk about how many conservative Democrats got elected last week, on the driving issue of the election — the war in Iraq — the energy and base of the Democratic Party is firmly on the far left. Over the next two years and in the 2008 cycle, Democrats will not have the luxury of running the same campaign they ran the last 18 months that culminated in Tuesday's sweeping victory.

A final, underappreciated dynamic of this year's midterms is what I have called "the fading 9/11 effect." The country's focus and concern over terrorism was a crucial factor that powered Republican gains in '02 and '04 as well as President Bush's own re-election. But five years of success in preventing terrorist attacks have bred complacency among the American public. The country simply doesn't take the threat as seriously when Bush pounds the table and insists we are at war with an enemy that is coming after us relentlessly. That is why the carefully orchestrated votes on detainee rights and NSA wire-tapping did not have the same electoral success they would have had 2-4 years ago.

This is a trend that will continue to work slowly in the Democrats' favor as the months and years go by without a major attack. But just like 9/11 substantively changed the political landscape five years ago, the next major terrorist attack will most likely shift the political winds dramatically back towards the Republicans as the public will have little tolerance for hand-wringing over terrorist "rights" and whether the Feds should take al-Qaeda phone calls to a FISA court.

Because 17 of the 29 seats Democrats won in the House were in districts Bush carried in 2004 by more than 5 percent, Republicans are not in as dire a situation as one might think based on recent news coverage. Though the size of their minority is very similar the Democratic minority elected in 1994, next year's GOP minority is in a much stronger position to recapture the House than the Democrats were in 1995.

Given the uncertainly with the situation in Iraq, the pursuit of nuclear weapons by Iranian President Mahmoud Ahmadinejad, and the possibility of another terrorist attack, it is hard to speculate too far into the future. But looking ahead to the presidential race in 2008, Democrats are still dealing with a post-Vietnam, George McGovern reputation on national security, which a liberal Speaker of the House from San Francisco is highly unlikely to change.

It's certainly possible Republicans will implode over the next 18 months and that vicious internal fights will only further alienate moderates and independents. But if the GOP can coalesce around a strong national-security nominee and a limited-government agenda in the Congress, they will be in good shape to rebound in 2008.