GOP Rep. Darrell Issa's retirement makes him the fourth Republican from a district carried by Hillary Clinton to not seek reelection in 2018. It's not as much of a game changer as Rep. Ed Royce's was yesterday because Issa was already highly vulnerable after winning by fewer than 1,700 votes in 2016, but it does put Democrats in the driver's seat to pick up the district.

The northern San Diego-county based seat voted for Clinton 50 percent to 43 percent, and Democrats already have several serious candidates, including Marine veteran/2016 nominee Doug Applegate, environmental attorney Mike Levin and EMILY's List-endorsed former State Department official Sara Jacobs, the granddaughter of Qualcomm's co-founder.

Republicans' best hope for holding the seat in the current lopsided political environment probably involves Democrats splitting the vote in the June top-two primary and allowing two Republicans to advance, but that would require a very elaborate set of circumstances. The race moves to the Lean Democratic column.