The U.S. Supreme Court has noted correctly that "the voters should choose their representatives, not the other way around." In Pennsylvania, which nominated candidates for Congress and state legislature in Tuesday's primaries, that is not how representative government has worked for many years.

At the beginning of this decade, Republicans drew legislative and congressional district lines so masterfully - and questionably - that the state's delegations don't come close to reflecting the population they're supposed to represent. Pennsylvania has about 4.1 million registered Democrats and 3.1 million registered Republicans. Yet Democrats have only 19 seats in the state Senate to Republicans' 30 (with one vacancy). In the lower house, Democrats have just 84 seats to the Republicans' 119.

The Washington delegation is even more lopsided: Of Pennsylvania's 18 House seats, only five are held by Democrats. There are other incongruities: The state's U.S. representatives include not a single woman and only one member of a minority group.

Of course, the candidates, their qualifications, and their records also help determine the winners and losers of elections. But in Pennsylvania and other states where gerrymandering goes unchecked, the playing field is tilted steeply in favor of the party in power. If Democrats seize control of the next redistricting, they can be expected to fix the districts similarly in their favor.

The results of rigged districts and distorted elections could be seen in Harrisburg's historic nine-month budget impasse this year. Most Pennsylvanians want the state government to fund public schools adequately, tax gas drillers, and end the state liquor monopoly. But politically extreme legislators derailed efforts to agree on anything significant.

Legislative districts designed to favor incumbents are part of the problem. Most Republicans' political challenges come from other Republicans, often on the right: The real races are in primary rather than general elections. The same problem exists for Democrats on the left. The result is that more extremists are elected and more moderates and independents are excluded.

Fortunately, a bipartisan bill backed by the good-government group Common Cause could reform the system. And there are political motives for cooperation on both sides: Democrats want more seats, and Republicans see a redistricting defeat on the horizon.

District lines are currently drawn by a commission that is evenly split between Democratic and Republican legislative leaders, with a tiebreaker chosen by the state Supreme Court. Republicans lost control of the court last year and with it control of the next redistricting.

The reform bill would create a bipartisan commission of qualified volunteers not beholden to the parties. Party officials, recent officeholders, and those aspiring to elected office would be barred. Relying on demographic, geographic, and other objective data, they would be required to draw more compact districts that reflect communities more rationally - unlike, say, the Seventh Congressional District, which sprawls through five counties from the Philadelphia suburbs to Amish country.

Speaker Mike Turzai and Senate President Pro Tempore Joe Scarnati should expedite the bill. Pennsylvanians' representatives should have to earn their votes.