Rep. Ken Buck‘s, R-CO, announcement on Tuesday that he will be leaving Congress at the end of next week has taken a narrow GOP House majority and put it on life support.

With Buck’s exit, Republicans will only maintain a 218-213 majority after next week, which is expected to shrink to a 218-214 majority when a special election is held to fill a vacant Democratic seat at the end of April. As Republicans look to avoid losing their thin House majority, here is when the GOP can expect reinforcements to bring their majority back from the brink.

Former Rep. Kevin McCarthy’s seat

The former House speaker left Congress on Dec. 31, 2023. His seat, California’s 20th Congressional District, is rated “solid Republican” by the CookPoliticalReport, with a partisan voting index of Republican +16.

Republican Assemblyman Vince Fong is favored to take the seat, having won the most votes in the general election primary last week. The special election primary to fill the seat for the remainder of the 118th Congress is set for March 19, with the general for the special election slated for May 21.

Former Rep. Bill Johnson’s seat

Johnson resigned on Jan. 21 to become the president of Youngstown State University after working in Congress for 13 years.

The seat Johnson walked away from, Ohio’s 6th Congressional District, is rated “solid Republican” by the CookPoliticalReport, with a partisan voting index of Republican +16, meaning it is highly unlikely to flip to a Democrat.

The special election primary is set for March 19, with a general election to be held on June 11.

Rep. Ken Buck’s seat

Buck’s sudden resignation came after he had announced he would not seek another term in November, and it moves up on the calendar when he will be replaced in Congress.

Gov. Jared Polis, D-CO, said on Tuesday he would set the special election “to align with Colorado’s primary on June 25,” though specific dates have not been issued by the governor.

Following Buck’s announcement, Colorado Gov. Jared Polis set a Jan. 25 election date.

Colorado law requires that a special election must occur no less than 85 days and no more than 100 days after the seat is left vacant, March 22. That timeline means the primary must occur between June 15 and June 30.