House Speaker Paul Ryan’s decision not to run for re-election, followed shortly after by an announcement from Florida Rep. Dennis Ross, brings the total number of House GOP retirements to 25.

That’s compared with only nine House Democrats who announced they will not seek another term.

Dozens more House GOP have resigned, announced runs for other offices or left for jobs in the Trump administration. 

As our colleague Dante Chinni writes, it’s “the highest number of retirements for a party in power for decades, surpassing the numbers in the wave election years of 2010, 2006 and 1994.”

Bottom line: The map only continues to get more difficult for Republicans defending their congressional majority.

Ross cruised to re-election in 2016 in a district that has been solidly Republican. But keeping Ryan’s seat in the GOP’s column may be a bigger challenge, especially considering what a symbolic victory it would be for Dems to claim the outgoing speaker’s seat.