Condition: Republicans control the U.S. Senate when the 120th Congress convenes on January 3, 2027: Republican senators hold at least 50 seats (with the Republican Vice President breaking ties). Otherwise this market resolves N/A.

Resolves YES if a lapse in federal appropriations causes a shutdown (agencies begin orderly shutdown procedures and furlough non-excepted employees) that starts at any time during calendar year 2027 (U.S. Eastern time), whether full or partial. A lapse that starts in 2026 and continues into 2027 does not count; one starting in 2027 counts even if brief. Resolves NO otherwise.

This is one half of a conditional pair; its twin asks the same question if Democrats win the Senate. Comparing the two shows what the market thinks control of the Senate changes.

Starting probability is a seed, not a forecast: anchored on public prediction-market prices where a related market exists, otherwise a prior.