Have Republicans actually managed to permanently steal the House of Representatives through gerrymandering, which is unconstitutional in the extreme?

Looks like it:

According to a Quinnipiac poll released today, if the election were held today 43 percent of the electorate would support a Democratic U.S. House candidate, as opposed to just 35 percent who would back a Republican. That 8 point lead for Democrats is significantly more than the GOP's margin of victory during the 2010 Republican wave election (6.6 percent) and even more that the Democratic margin of victory during the 2006 wave (7.9 percent) -- when Democrats were bolstered by both an unpopular Republican president and a failing war in Iraq. And yet, if Democrats succeed in maintaining this substantial lead through next year's congressional election, they will likely emerge with a tiny majority of just 5 seats.

[...]

Indeed, Republican gerrymandering was so successful during the last redistricting cycle that Democrats would likely need to win the national popular vote by more than 7 points in order to win the barest of majorities in the House.

The old rule of thumb based on hundreds of years of election results is that winning 51% or more of the total votes for all House races virtually guaranteed winning a majority of the seats.

Republicans changed that in 2010 and have redrawn districts so politically and so effectively that as TP notes and I'll put it in reverse, Republicans could lose the popular vote for the House by almost 7 points and still retain a majority of the seats and control of the chamber.

Forget voter fraud, there's virtually none of that in America. This is election fraud, this is the GOP stealing not just elections, but control of an entire chamber of Congress. Democracy isn't being threatened by taking away your guns, it's already been taken away via gerrymandering, and it's Republicans who stole it from you.