Here's more evidence that the rigged redistricting process — in Wisconsin and across most of the nation — needs reform.

The number of swing seats in the 435-member House of Representatives has fallen by 40 percent over the last two decades, according to Cook Political Report, a nonpartisan analyst of elections and campaigns.

Cook's calculated that voters in 159 congressional districts could favor either major political party before the 2000 elections. That dropped to 104 swing seats by 2010. And Cook's expects just 96 will be competitive in the coming fall elections, USA Today reported.

Partisan redistricting — in which the state politicians in power get to draw new voting district boundaries to their liking after a major census — deserves a lot of the blame.

In Wisconsin, the Republicans who run the statehouse in Madison just redrew our eight congressional districts.

They tried to shore up U.S. Rep. Tom Petri's 6th Congressional Seat for potential GOP successors, said David Wasserman, who analyses House races for Cook's. Petri, R-Fond du Lac, has held the seat since 1979. Petri's district is now trending more Republican, in part because of boundary changes that pulled in more conservative-leaning voters, Wasserman said.

At the same time, the new GOP-drawn Wisconsin maps surgically remove the Democratic-leaning cities of Stevens Point and Wisconsin Rapids from the 7th Congressional District so vulnerable freshman Rep. Sean Duffy, R-Weston, will have an easier time holding his seat. The change also makes U.S. Rep. Ron Kind, D-La Crosse, much harder to beat. His 3rd District absorbed the Democratic turf.

"Duffy now has more than a fighting chance of winning re-election, and Kind could be congressman for life," Wasserman told the State Journal on Monday.

The GOP map designers also gave U.S. Rep. Paul Ryan, R-Janesville, a somewhat more conservative-leaning 1st Congressional District.

Wasserman said some of the reduction in swing seats nationally results from more voters choosing to live in communities that agree with them politically. But that only makes it easier for politicians to partition voters into lopsided districts, "because voters have already self-sorted themselves," he said.

There's a better way: California, for example, selects a citizen panel (using a lottery and vetting by its state auditor) to draw new voting district lines.

"If replicated (in Wisconsin), there would certainly be more competitive districts," Wasserman said.