Does increased urbanization hurt the Democrats in the House?

[Sbane]

Not necessarily. A dense urban area can be used to send districts from the city out into the suburbs neutralizing GOP votes. IL Dems did that very effectively this cycle. They added two seats out of 18 compared to a neutral map. On the flip side the GOP can use the urban packing against the Dems as in OH.

Yes, but what about in a neutral map?

[Sbane]

Republicans effectively packed Democrats into hyper-urban districts in MN, WI, MI, IN, OH, PA, and VA and divided the rest of the state almost on an at-large basis. Such is effective for giving an edge to just about any Republican politician because in the extra-urban districts (including some with liberal-leaning cities like Kalamazoo, Lansing, and South Bend that can be effectively diluted with rural votes) the district might have a 54-46 split in Presidential elections.

The hazard for Republicans is that they could get just about any Republican elected, including some people very far to the Right on the political spectrum. Winning the Republican primary would be all that matters, and as the Republican Party goes increasingly to the Right, so do the Republican nominees for the House in the rural and semi-urban districts. But such nominees can eventually offend the sensibilities of such moderates as there are. We may see a Democrat well suited to a D+4 district defeating an incumbent  Republican well suited for an R+40 district in R+5 (Cook PVI) districts in many districts that Republicans gerrymandered to the immediate benefit of Tea Party pols.

Republicans may have gotten some poisoned wins in 2010.       

MN was drawn by the court.

There are arguably more districts where Dems dominate and the primary is the only election that matters. Those districts should pull to the left as much as the solid Pub districts pull right.

And yet you don't see that happening. No one is out there advocating socialism. The Republican primaries on the other hand are full of crazy wingnuts.

To an extent I do believe in the cyclical theory of politics. Just like the Democrats overreached in the 1960's and 1970's after dominating the landscape since the 1930's, we are seeing Republicans overreaching now. That is why you see purity tests being held in R+5 districts while moderates are running without problems in D+15 districts.

[Sbane]

In terms of gerrymandering and vote packing. Does the denser population in the Democratic cities help the Republicans, who are more spread out among the metro fringe and the rural areas?

Yes, but the problem isn't population density as much as the fact that you might have a city that votes 70% Democratic surrounded by suburbs that vote 55% Republican. With a map that doesn't visually look gerrymandered, the city is a Democratic vote sink while Republicans win the suburbs.  A fair map should look a little gerrymandered for the Democrats. A map that is drawn heavily in favor of Democrats, like this one, ends up looking epic.

http://www.swingstateproject.com/diary/6166/

That is assuming you think a fair map should necessarily be balanced between Republicans and Democrats.