The following is an edited transcript of an interview with David Wasserman, the House editor of The Cook Political Report. Mr. Wasserman is Cook’s resident redistricting expert and the author of “Better Know a District,” the The Cook Political Report’s 2012 redistricting outlook. (Readers might also want to check out Cook’s redistricting scorecard for background).

We will post the conversation in two parts, this being Part 1, which focuses on the more general aspects of redistricting. Part 2 will focus on more granular details at the state and local level. The interview was conducted by Nate Silver and Micah Cohen.

MC: Can you just talk generally, for someone who is not following redistricting at all, about what we should expect?

DW: Democrats are poised to gain a handful of seats. The inimitable Stu Rothenberg put out a great column outlining why the pendulum has swung in a minor way toward Democrats, and why they’re poised to pick up a handful. And I agree with his assessment.

If you take what Democrats need to get to the majority, they need 24 more seats after picking up New York 26. Their best case scenario is a gain of 4 to 5 seats total from redistricting – assuming things go their way in court in Florida and some of the other big states where there’s a lot on the line. Then they need 20 more seats after that to get to a majority.

But the effect of redistricting is to make those 20 seats a little more difficult for Democrats to gain, because Republicans will be able to shore a lot of them up. There are 61 Republicans – including many, many freshman – who are sitting in districts carried by President Obama in 2008. A third or 40 percent of those Republicans stand to benefit from redistricting and will get better seats. Whether it’s enough for some of them to stave off Democratic challenges is a question we’ll have to answer next year. But those next 20 seats get harder for Democrats as a result of redistricting.

Republicans have unprecedented control over the state legislatures that will draw the lines. They control the process in states with 202 house districts compared to just 47 for democrats. But the irony is that Republicans made so many gains in 2010 that they don’t have a lot left to gain. They simply have a lot left to shore up.

NS: The way I envision is a graph where you have the generic ballot on one axis and the net impact on the other. If you had a political environment that resembles the one you had in 2010 then Republicans might break even or Democrats might gain a couple of seats. But Democrats will find it more challenging if you were at that threshold where they were a couple of points ahead on the generic ballot; they might be hurt there, right?

DW: Right, absolutely. The bottom line is that if the political environment is great for Democrats in 2012, then a lot of Republican gerrymanders will end up looking like dummymanders. Whereas if the environment is neutral or Republicans have a slight advantage, then Republican maps will look brilliant. That’s the nature of this game.

NS: How different would the results be if Democrats controlled the majority of state legislatures instead of Republicans? Maybe there are some structural factors that are making this, I guess, better for Democrats than conventional wisdom might hold. But could they have made really big gains if they’d won a few more states?

DW: Oh, absolutely. Because Republicans have so much to lose in this process. If Democrats were in control in all of these big states then we’d have lots of Illinois scenarios, where you have a lot of Republican freshman on the line, and Democrats can basically take a weed-whacker to their districts, and cut them however they want to. And in Illinois alone, Democrats are poised to pick up 4 or 5 seats. If Democrats were in control in Ohio as well, they could pick 4 or 5 seats in Ohio, same with Pennsylvania. That would be the House majority right there.

NS: So let’s talk more about which states have been most important in this process.

DW: For Republicans, the key state is North Carolina, for a couple reasons. No. 1, it was a Democratic-drawn map in 2002. No. 2, there are plenty of Democrats who survived in North Carolina in 2010. And No. 3, the governor is the only Democrat in a position of power in North Carolina, and she doesn’t have veto power over the redistricting map. (Actually that was a rule that Democrats designed back in the day to try and prevent Republicans from getting control.) So Republicans are likely to pick up three seats in North Carolina.

And then on the Democratic side, their big prize was Illinois. They were able to pass a map that gives them a shot at picking up 4 to 5 seats.

And California’s new citizen’s commission is likely to unravel the incumbent-protecting-gerrymander that was passed in 2002 and hand Democrats a couple of seats. So you kind of take the states that are gaining and losing seats and add it all up and there’s no question that California and Illinois are big prizes for Democrats, even if they don’t have exclusive power to draw the map in California.

NS: Are there any other states on the G.O.P. side that could become like North Carolina? Which state is best for them after North Carolina?

DW: Well, Georgia is a great state for them. They’re going to draw the new seat in Georgia for themselves. They can also draw John Barrow , the only white Democrat left in Georgia, out of a seat.

Republicans are also set to pick up seats in Indiana, in Utah, in South Carolina and several others. Where Democrats may gain some seats in Nevada and Washington, and obviously California and Illinois.

NS: How far does a party want to go to protect incumbents? I’ve heard that said that they want build districts where they won 55 percent of the presidential vote — that’s kind of their optimal number. Is that a good general rule of thumb?

DW: Well, the yardstick is different from state to state. In Illinois, for example, Democrats wouldn’t be comfortable just drawing a 55 percent Obama district because of the native son effect. In Texas, for example, Republicans want to draw some districts in excess of 65 percent for McCain because Democrats like Chet Edwards have been competitive in the past in very Republican territory. So the yardstick is different from state to state.

All we can be sure of is that this is going to be a once-in-a-decade nerdfest for pundits, politicians, lawyers, academics, demographers, cartographers and hobbyists, all trying to show members of their party how best to maximize their advantage through the redistricting process.

MC: What’s the time frame for how this plays out, including the legal aspects? Is it drastically different from state to state?

DW: Every state is on their own timetable. The first eight states that have already finished the process this year are almost exactly the same set of states that finished the process first last time around in 2001 and back in 1991 Iowa is one of those states. Indiana is another of those states.

But there are some states that traditionally don’t start redistricting until the year of the election. New York is one of those states. We wont know what goes on in New York for quite some time. And [in some states], litigation will drag this process out beyond next year’s elections. Some maps, just like last time, will be in court until the middle of the decade.

MC: In terms of gerrymandering, is there a shame factor that constrains how far a party is willing to go? Or are they going to push it as far as they want?

DW: There is a certain threshold at which voters react badly to excessive gerrymandering. We saw that in Georgia in the earlier part of the last decade where Georgia Democrats engineered a gerrymander that looked like a Jackson Pollack painting. Democrats failed to achieve the kind of gains that they were hoping for in that map in part because voters rejected the way in which the lines were drawn and saw it as a Democratic power grab.

You’ll notice that in Illinois this time around, Democrats could have drawn lines that were even more mangled than the ones in effect right now. But they chose not to, and actually part of the brilliance of it was that the districts they produced, at least downstate, were relatively compact by gerrymandering standards.

NS: There are some other constraints, right? You hear about compactness. You hear about contiguity. What practical constraints do they place on the process?

DW: All districts have to be contiguous. Compactness is a different matter all together. Mathematicians and geometrists have attempted for years to come up with a uniform way to calculate compactness. But there is really no one-size-fits-all solution to evaluating whether a map is compact or not. If there were, courts would probably be drawn to it.

An underappreciated fact about congressional elections is that Congress, in the Constitution, has the ability to regulate the election of its members. And Congress could theoretically establish a bill to curb gerrymandering in congressional elections by imposing limits on the number of times you can split political subdivisions. That actually took the form of a bill sponsored by former Congressman John Tanner for many years. But now John Tanner is out of the House. And there are very few members of Congress with the political willpower to tie their allies’ hands.

NS: Another constraint is the need to create or preserve minority districts. I’ll be honest, I can find this stuff confusing. For example, in New York, how might those rules be applied when you’re losing two seats statewide?

DW: It’s commonly understood among members of both parties that unnecessarily eliminating a majority minority seat is like swatting at a hornets nest, in a legal sense. That under Section 2 of the Voting Rights Act, if a minority group can form a sufficient majority in a compact district then they’re entitled to that district.

In New York, there’s some districts that are untouchable even though it’s not one of the states that’s covered by Section 5 of the Voting Rights Act. For example, in Harlem, even if Charlie Rangel were to retire, the historic nature of his district makes it all but impossible to eliminate. The same can be said for both African-American majority districts in Brooklyn and the black majority district in Queens, the Hispanic-majority district in the Bronx and the one straddling Brooklyn and Queens.

I should add that when the number of seats in a state changes those benchmarks tend to go out the window, and courts evaluate the extent to which minority districts can be drawn in a map with a new number of districts.

For example in South Carolina, there is going to be an interesting test of the Obama Justice Department’s willingness to interpret provisions of the Voting Rights Act in Democrats’ favor. Theoretically it is possible to draw a new map with two majority African-American seats in South Carolina as opposed to one. Legislators in South Carolina will likely draw a new Republican seat instead of a new African-American seat, but what will the Obama Justice Department have to say about that? The Justice Department’s rulings are one of the most important wild cards in this process. We don’t know what they’re going to do.

MC: How much impact does the White House have on this?

DW: The party in the White House makes a difference only because the Justice Department has the authority to issue pre-clearance under Section 5 of the Voting Rights Act. And this is a new frontier for redistricting because every redistricting round since the passage of the Voting Right Act has taken place under a Republican administration: Nixon in ‘72, Reagan ‘82 and the Bush justice departments of ‘92 and 2002.

NS: Would you expect the Justice Department to make an explicitly partisan calculation, and try to weigh ‘could this do damage to President Obama’s brand?’ against ‘here’s how many seats we might gain.’ Or are they more pure-of-heart than that?

DW: Keep in mind that the Justice Department’s voting section is staffed by many career attorneys, whose opinions on minority voting rights have been overruled by political appointees in the past. Their thought process on redistricting predates any thought process that came into play with a new Justice Department in 2009. We simply don’t know where they’re going to pick their battles.

NS: When parties are thinking about redistricting, are they thinking about the whole 10-year period or are they just thinking to the next election?

DW: Parties have traditionally been pretty short-sighted in redistricting, and there’s some evidence of that again this year. But I’d say more than in past years the consultants and strategists are thinking about the long term. Because there have been three consecutive wave elections, there is really a sense among them that they need to think long term about safeguarding the districts that they draw. So we’re seeing Republicans place an emphasis on simply shoring up their gains and not trying to cut their advantage too thin. I hear some consultants talking about software that assesses not only the political performance in districts, but the overall trend line over the past ten years to gauge which direction districts are moving. That’s a new wrinkle in this process that wasn’t really present ten years ago.

NS: What mistakes can parties make? Can they get bad advice? Are there consultants out there who don’t know what they’re doing?

DW: Balancing competing interests of incumbents with partisan considerations, overall strategy and Census data is really, really difficult.

One possible mistake early on in this process is Texas Republicans’ decision to put forward a map that lacks a second new Hispanic-majority district. It’s possible that they could have drawn a map that created the same number of Hispanic majority seats that MALDEF, the Hispanic advocacy group, wanted, and still preserved their grip on the seats that they have. But because they have shortchanged the number of Hispanic districts, it’s possible that their entire map might get thrown out in court, and that’s a risk that Republicans might not want to run.

So it’s possible that some parties will go too far in the process. But for the most part, there are so many consultants and so much data in the room, that parties really are going through every scenario and feverishly coming up with a plan that maximizes their opportunities.