Republicans have gotten a redistricting reality check in recent weeks.

First, Democrats in Illinois passed a new congressional map that targets half a dozen Republican seats. Then the California redistricting commission released a draft map that could claim three or more GOP incumbents. Iowa and Louisiana, meanwhile, have drawn maps where Republicans could very well lose one seat each.

In short, the states that have been first to move in the decennial process of drawing new districts have actually set up Republicans to lose seats — upwards of 10 so far — in a redistricting cycle that was supposed to be so good for the GOP.

And it’s got smart political analysts questioning just how much of an edge Republicans actually have in redistricting. Despite controlling the re-drawing of four times as many seats as Democrats, they point out, it looks like Democrats will be close to equal with the GOP when it comes to creating new and winnable districts.

Because of this, Democrats including Democratic Congressional Campaign Committee Chairman Steve Israel (D-N.Y.), have been suggesting for months now that redistricting would be “a wash.”

And we’ve written about how he’s right — in a way. But there’s more to the story.

In fact, Republicans still have an advantage when it comes to redistricting, and that’s because of two things. One, they can make many of their most vulnerable members safer. And two, they already control the vast majority of marginal districts, which has the effect of masking any redistricting advantage that they actually enjoy.

As it stands, the reality of the national map is preventing Republicans from expanding beyond where they are right now. But what about the other big aspect of redistricting — shoring up their members?

This is the one big advantage the Republicans have — a fact they’ve increasingly been emphasizing as it’s become clear they won’t be able to expand the map much, if at all. Republicans privately acknowledge that they failed to emphasize this part of the process early on, and now they’ve got to contend with an unhelpful narrative that they oversold their advantage.

“It doesn’t have the sex appeal to be consolidating gains instead of taking out incumbents,” said Chris Jankowski, president of the Republican State Leadership Committee, adding: “I can understand why Democrats in Washington are trying desperately to look for good news, but they’re stretching it when it comes to redistricting.”

At the same time, however, their ability to shore up their members is also somewhat limited.

Take Pennsylvania. Republicans have a half dozen vulnerable members there. They insist they will be able to help all of them, but several of those members — specifically Reps. Jim Gerlach, Pat Meehan and Mike Fitzpatrick in the Philadelphia suburbs — are likely to see their districts get only marginally more friendly. That means they will still be Democratic targets in 2012.

The same is true in a few states that have begun moving on their redistricting. While a draft map in Wisconsin would help freshman Republican Rep. Sean Duffy, it can only do so much, and other marginal districts held by GOP Reps. Paul Ryan and Reid Ribble, for example, get little or no help.

In Indiana, Republicans finished work on a map that will help freshman Rep. Todd Young (R) but may actually complicate matters for freshman Rep. Larry Bucshon (R) slightly. In Michigan, a draft proposal helps Reps. Thaddeus McCotter some, but doesn’t add many Republicans for freshmen Reps. Dan Benishek and Tim Walberg, though it does draw former Rep. Mark Schauer out of Walberg’s district.

“There is almost nothing House Republicans can do to protect their vulnerable incumbents in redistricting when the voter growth in those districts and their neighboring districts comes from Democrats,” said DCCC spokesman Jesse Ferguson.

According to a Fix analysis, in the 17 states where Republicans control redistricting, they can shore up about two dozen potentially vulnerable members. And, if new redistricting restrictions in Florida don’t prevent them, they can do the same for another half dozen seats in the Sunshine State.

That’s 30 seats that could become better for Republicans — even if marginally so in a lot of cases.

Compare that to Democrats, who have very few districts to shore up in the states where they control redistricting (less than five), and it’s clear that this where the GOP’s true advantage lies.

Most of those GOP members, though, will continue to be targeted by Democrats because their districts will still be marginal. And the ones that can get a lot of help generally come in districts that Democrats weren’t counting on targeting anyway — many of them in the South.

So while Republicans will likely be able to give themselves a better map nationwide, it won’t be that much better.

Better is still better, though, and when you’ve already got almost all the marginal districts in your camp, that’s a very good thing.

If Republicans had the same numbers of seats as Democrats instead of having a 47-seat majority, it would be pretty clear that they have a redistricting advantage. That’s because there would be many more marginal districts for them to change to their liking.

As it stands, they’re trying to expand on their biggest majority in 60 years, and even when you are pulling most of the strings in redistricting, there’s only so much you can do.

Redistricting is not a zero-sum game. While we can make guesses as to what a map means for either party, until elections actually occur, we don’t really know anything. What looked like a great map for Republicans in Pennsylvania 10 years ago, for example, turned into a very good map for Democrats by the middle of the decade, when they won a slew of districts that were drawn to marginally favor the GOP.

While much of the coverage of redistricting focuses on who can add winnable seats in a given state and how many, Republicans have begun to acknowledge that goal No. 1 for them is to keep what they’ve got.

If they can do that, it will be a victory for them. It just won’t be the huge, game-changing victory that some expected.