Here is a breakdown of voter registration totals — an important statistic for each race.

The numbers below are broken down by district, or statewide for the Senate race, and by party registration — Democrat, Republican, no party, or other (voters in Iowa can register with the Green and Libertarian parties).

Voters in Iowa must be registered as either a Democrat or Republican to vote in the party’s primary, although voters can change their party affiliation on primary day.

SENATE (STATEWIDE):

Democrats: 613,720

Republicans: 636,716

No party: 672,363

Other: 6,519

FIRST DISTRICT:

Democrats: 160,118

Republicans: 139,960

No party: 180,519

Other: 1,616

SECOND DISTRICT:

Democrats: 169,728

Republicans: 144,347

No party: 170,811

Other: 1,697

THIRD DISTRICT:

Democrats: 160,444

Republicans: 168,563

No party: 155,453

Other: 2,066

FOURTH DISTRICT:

Democrats: 123,430

Republicans: 183,846

No party: 165,580

Other: 1,140