Legislators seem to always need a hard deadline for anything important, and now they have one: the Connecticut Supreme Court today set a final deadline of noon on Dec. 21 for the legislature’s redistricting commission to produce a map of new congressional districts.

The legislature got the census data necessary to draw the maps in March, but the redistricting panel missed deadlines of Sept. 15 and Nov. 30. Now, if the panel fails by the winter solstice, the shortest day of the year, the court will draw the district lines for the first time in state history.

Last week, the panel unanimously approved new districts for 151 state House and 36 state Senate districts, but its only joint work on the congressional districts involved the Democrats and Republicans exchanging very different maps.

Democrats handed in a map that preserves the existing districts, making only small adjustments necessary to balance the population in each of the five districts.

Republicans proposed major changes that would eliminate the oddly drawn border of the 1st and 5th districts, the result of a bipartisan compromise 10 years ago to accommodate two incumbents no longer in Congress: Democrat James Maloney of Danbury and Republican Nancy Johnson of New Britain.

But the GOP plan is more than an exercise in asthetics. Its map would transform the 4th District, now represented by Democrat Jim Himes of Greenwich, into a GOP stronghold and improve the party’s chances in the 5th, which will be open next year.

The new state legislative districts already are shaping the 2012 election lineup in the state House: Two Democrats who found themselves politically homeless after the Assembly districts were approved are not seeking re-election.

Roy announced his decision in a press release today. Kirkley-Bey has scheduled her announcement and a reception for Wednesday at 11 a.m. in the Old Judiciary Room of the State Capitol. Both were elected in 1992 and are closing in on 20 years in the legislature.

“My wife and I have been discussing the possibility of not running again for many months,” Roy said. “The results of the redistricting effort just made my decision easier.”

Kirkley-Bey could not be reached for comment.

Their districts — the 5th Assembly for Kirkley-Bey, the 119th Assembly for Roy — will be open seats next year. Under the new map, Kirkley-Bey’s home will be in the 1st, which heavily favors Rep. Matt Ritter. Roy will be in 117th, where Rep. Paul Davis is the favorite.

The one-paragraph order issued by the court today gives no hint of what’s to come if the Democrats and Republicans cannot agree on a new congressional map.

Would the court simply choose between the Democrats’ map and the GOP’s? Would it appoint a special master charged with drawing a third version? Could outside groups weigh in with their versions?

All five seats — slow population growth cost a seat in 2001 — are now held by Democrats, meaning there is little downside for the GOP to roll the dice by giving the Supreme Court a shot at drawing new congressional districts.

No substantive talks took place since the passage of the Nov. 30 deadline.

“I thought the Democratic proposal made a lot of sense,” said U.S. Rep. John B. Larson, D-1st District.