Topeka ? A divided Kansas Senate on Tuesday approved new Senate district boundaries in one of the most contentious debates of the 2012 legislative session.

The measure passed 21-19 with moderate Republicans and Democrats teaming up against conservative Republicans.

Moderate Republicans made amendments to draw district lines that would allow two conservative GOP House members to challenge two moderate Republican senators in the August primary.

But conservative senators, House members and Gov. Sam Brownback have said they wanted more changes.

An attempt to redraw district lines to force a face-off between Sens. Marci Francisco of Lawrence and Tom Holland of Baldwin City failed. And an attempt to save a western Kansas district also failed.

Senate Redistricting Chairman Tim Owens, R-Overland Park, referred to demands from Brownback and House Republican leaders as the “800-pound gorilla in this room.”

He said that as a concession to them, both he and state Sen. Jean Schodorf, R-Wichita, proposed amendments that redrew district lines, allowing potential conservative Republican opponents to take them on.

During the nearly three-hour debate, potential House challengers to senators and Brownback’s staff crowded the side aisles of the Senate.

Schodorf said the House was holding hostage a number of issues, such as the budget and school funding, until the Senate approved a district plan. Owens said he didn’t like redrawing a map to accommodate his expected opponent, state Rep. Greg Smith, R-Overland Park, because it violated communities of interest. But he was doing it, he said, because House and Senate leadership had made a deal to try to resolve redistricting.

Later, House Speaker Mike O’Neal, R-Hutchinson, denied he made a deal.

Owens’ proposed map also added a senate district in Johnson County because of the growth there, and collapsed a western Kansas district that has been losing population.

State Sen. Steve Abrams, R-Arkansas City, proposed a map that would have kept the western Kansas district.

“Kansas is a rural state,” he said.

Owens said he sympathized with the concerns of western Kansas, but there was a 93,000 increase in population in Johnson and Wyandotte counties and those concerns “need to be addressed as well.”

Abrams’ map failed 19-21, and then Owens’ was approved.

The Senate bill also includes the measure that the House already approved for its district lines, and the new boundaries for State Board of Education districts.

Owens said he hoped the House would approve the Senate plan just as the Senate approved the House plan.

“If we fail there, we will be in conference committee. And if we fail there, then we will be in court,” he said.