Louisville, Ky. ? Three out of five Americans eligible to vote won’t cast ballots in the congressional elections on Tuesday. By choosing to stay away from the polls, these nonvoters will contribute more to divided, 50-50, deadlocked government than citizens who participate in the democratic system.

If they voted, disengaged Americans might or might not tilt national politics decisively toward Democrats or Republicans, giving one or the other enough strength to govern. But by broadening the pool of engaged citizens, their participation would dilute the power of the two relatively small partisan factions that are choosing our political leaders, making government shriller and more polarized than ever.

Widespread voter alienation leaves the nation’s politics to be driven by activists with narrow but passionate interests. Unions, African American ministers, environmental groups and abortion-rights organizations mobilize Democrats. Business interests, conservative Christians, anti-abortion and anti-gun control groups motivate Republicans.

This division “turns out people who have the strongest partisan views, and the views that are the most ideologically polarized between the parties,” said Thomas Mann, an election expert at the Brookings Institution, a center-left think tank in Washington. “Non-voters have weaker partisan attachments, they are less ideologically polarized and more amenable to swing one way or the other, depending on national conditions.”

The result is government split almost exactly between Republicans and Democrats ruled by a president who failed to win a majority of the popular vote, a Congress divided almost evenly, 49 state legislative chambers run by Democrats and 47 by Republicans, and, after Tuesday, a probable near-even partisan balance among 50 governors. The near-even balance of power often dead-ends in stalemate.

Tuesday’s voter turnout is expected to be the lowest in 56 years. The relationship between non-voting and gridlock can be self-perpetuating, as deadlocked politics yields ever more voter disengagement.