HARRISBURG — More than 1.2 million registered voters can’t take part in Pennsylvania’s “closed” party primary elections. A bipartisan pair of state senators say changing that is crucial to restoring healthy political discussion.

Sens. Lisa Boscola, D-Northampton, and Dan Laughlin, R-Erie, on Wednesday introduced a bill to allow voters not affiliated with the two major parties to cast ballots in party primaries. Doing so, they said, would force Democratic and Republican primary candidates to reach out to a broader swath of voters, instead of courting only the extreme right or extreme left of the electorate.

“In Pennsylvania politics, thanks to these closed primaries, spring is not a time when hope flowers, but when apathy, cynicism and polarization take root,” Mr. Laughlin said at a Capitol news conference. “Let’s be honest, our primary process no longer works.”

Ms. Boscola said she has unsuccessfully pushed bills for 20 years that seek to end “closed” primary elections limited to Republicans and Democrats. This latest attempt, she said, may have a better chance at success because the number of people who consider themselves politically independent is growing.