Two Wisconsin state senators have introduced SB 250, which would end political party nominations for U.S. Senate and U.S. House. Instead, all candidates for those offices would appear on a single primary ballot, and then only the top five candidates could appear on the November ballot. The November ballot (but not the primary) would use ranked choice voting. Here is the text. The bill has 20 co-sponsors in the House. It was introduced March 25, and has not yet had a hearing.

If enacted, the bill would probably result in a complete absence of minor party candidates on the November ballot for U.S. Senate, because there are always so many Democrats and Republicans that run for that office, minor party candidates can’t place in the top five. But for U.S. House, there would be some districts in which a minor party candidate did qualify for the general election ballot, because not as many major party figures run for U.S. House.

California and Washington have had top-two systems, and the data from these two states can be used to predict what would have happened if those states had top-five systems instead. No minor party candidate in California or Washington has placed as high as fifth for any U.S. Senate primary, in the history of their top-two systems. There have been seven US Senate primaries in the two states:

Washington 2010: highest minor party candidate, a Reform Party member, placed 12th
California 2012: highest minor party candidate, a Libertarian, placed 9th
Washington 2012: highest minor party candidate, a Reform Party member, placed 8th
California 2016: highest minor party candidate, a Libertarian, placed 10th
Washington 2016: highest minor party candidate, a Libertarian, placed 6th
California 2018: highest minor party candidate, a Libertarian, placed 15th
Washington 2018: highest minor party candidate, a Libertarian, placed 12th