Editor’s note: Not all congressional races are created equal, and Roll Call’s politics desk admits to playing favorites. So in the spirit of the holidays, these are a few of our favorite things (races) to cover this cycle. We’re shining a spotlight on our 12 most fascinating races through the new year — in no particular order. Happy holidays from @RollCallPols!

Not much stands in the way of Democrats picking up California’s 31st District this cycle — except themselves. Again.

By the numbers, the district marks the best opportunity in the entire country for Democrats to pick up a House seat. Rep. Gary G. Miller holds dubious distinction of being the Republican representing the strongest Democratic district in the country.

But this race continues to be fascinating because, so far, Democrats have not learned their lessons from a 2012 upset here. Last cycle, several Democrats split the vote in California’s “top two” primary system, allowing Miller and another Republican to proceed to the general election.

This cycle, one Democrat will likely make it through the primary, along with Miller. No other top Republican has announced a bid for the seat.

But a divisive primary is the last thing the party needs in a district that Democrats should easily pick up. President Barack Obama carried the seat with 57 percent in 2012.

Four Democrats are running in the primary, including the Democratic Congressional Campaign Committee’s pick, Redlands Mayor Pete Aguilar, and an EMILY’s List-backed attorney, Eloise Gomez Reyes.

The primary took an ugly turn this summer, when former Rep. Joe Baca, D-Calif., and Gomez Reyes engaged in an endorsement war. Baca lost re-election in a nearby district, and now he’s aiming for a comeback in the 31st District — against the wishes of some party leaders.