Last week, I evaluated the Republican candidates for president on their capacity to bring about change — in tone, in interaction with Congress, in policy. This week, I will reflect on the Democrats, in the context of the broader dynamics of the political system, and what a Democratic president would likely face in next year’s Washington.

[IMGCAP(1)]Let’s begin with the context. It will be a very tough environment. First, the ideological divide between the parties will be even greater than it is now. A majority of the 29 House Republicans retiring are either moderates or members of the problem-solving caucus — inclined, whatever their ideology, to work across the aisle to find solutions. Only a handful of House Democrats are departing, nearly all to run for the Senate, and they tend to be moderates also — and now we have to add in the tragic loss of Rep. Tom Lantos (D-Calif.). The vulnerable House Members in both parties also tend to be moderate Republicans and the more centrist Democrats. The departure of GOP Senators such as Chuck Hagel (Neb.), John Warner (Va.) and Pete Domenici (N.M.) also will reduce the problem-solving center there, and more like them may lose in the fall.

Second, the Republicans are not likely to be in a mood to be conciliatory if they lose the presidency. Once again, as in 1993, they will be shut out of power. A Democratic victory means the virtual certainty that Democrats pick up seats in both chambers. Even with the gains, though, Democrats would have fewer Members in either chamber than they had in 1993.

The same challenges will face a Democratic president, including the difficulty getting anywhere close to the discipline among Democrats in Congress that George W. Bush enjoyed in his first term with his Republicans. Democrats just do not have the same culture of loyalty to the party cause or the president, and tensions between the left of the party and the remaining core of centrists will be high. Cross-party coalitions will be necessary.

Can either Sens. Hillary Rodham Clinton (N.Y.) or Barack Obama (Ill.) navigate this political minefield and bring about serious policy change? Clinton has two major assets to bring to the table if elected. First, she was there when that similar and difficult dynamic was present and will be neither surprised nor unprepared. And her years in the Senate have shown a feel for the legislative process and an ability to work with her colleagues that is impressive.

Clinton has been a model Senator, but her history in Washington has left her with a distinct polarizing aura. To be sure, it is less true in Washington, where she has built relationships with many of the most conservative and even dogmatic Republicans, but it is distinctly true out in the country and in the conservative media and blogosphere. They will help color the atmosphere in D.C. and the willingness of Republicans inside the Beltway to join with her.

It also is an open question as to whether Clinton can integrate the lessons learned from the health care experience in 1994 to create a different outcome. Her current plan is carefully drawn to avoid the drawbacks of the earlier one, and in no way fits the stereotype of “Hillarycare” used repeatedly by Mitt Romney. If anything, this Clinton plan is very much like the “Mittcare” plan in Massachusetts. But a hard push early for mandatory universal health insurance is risky — it could end up rallying Republicans in opposition and might not get united support from Democrats. (Sound familiar?)

What about Obama? His tenures in the state Senate and on Capitol Hill both have shown a willingness and an ability to work with Republicans. One of the more striking collaborations was with Sen. Tom Coburn (R-Okla.) on a successful effort to put all federal contracts online. His work on lobbying and ethics reform was exemplary, and his health care plan has been criticized by many liberals for falling short of universal coverage but has a better chance to achieve cross-party cooperation.

Obama’s great strength is in his ability to communicate his vision of change and to move beyond the old divisions. He has no history of getting caught up in tribal divisions, and he might be able to use the early glow of a honeymoon to build some broad coalitions in a handful of important areas, particularly since voters will have said, “We want change and problems solved.”

But in the end, the ability to pass major legislation will depend on how skillfully he or she exploits the months immediately after the election to counter the divisions and build positive momentum. Clinton might learn from her husband’s experience and start fast in November, getting her appointments from deputy assistant secretaries to White House staffers to Cabinet secretaries moving early to have a real government in place on Jan. 20. Obama would move quickly to pick key Republicans to fill some important policy positions, creating genuine prospects for cross-party and cross- institutional cooperation. Both, in their Senate staffs, have shown good judgment picking people and real leadership keeping them, something that would carry forward to the White House.

Over the next few weeks, in debates or other settings, they should both be pressed on these topics: What are your plans to operate in the continuing corrosive atmosphere in Washington? How would you organize your administration from Nov. 5 on? What will you do in the first 100 days after Jan. 20? And what would you do in the first six months to change the tone and the outputs?

As of yet, we do not have adequate answers to these critical governing questions.

Norman Ornstein is a resident scholar at the American Enterprise Institute.