Pennsylvania GOP Rep. Keith Rothfus has been abandoned by his would-be allies in a tough race.

As we enter the stretch run of the 2018 midterms, we're rolling out a new spreadsheet that attempts to track which House races the big-money players have decided to triage—either because they feel supremely confident, or because they've concluded their candidate is doomed. These developments, however, are very tricky to stay on top of. That's partly because data on TV ad reservations, which is the best tell, can be fragmentary. Major outside groups can also change their minds and jump back into a race they'd previously abandoned.

Then there's the fact that, in the post-Citizens United era, the party committees that used to call the shots now compete with giant super PACs—at least on the GOP side. To date, the Congressional Leadership Fund, which is closely linked to House Speaker Paul Ryan, has spent about $64 million this cycle, twice the $32 million spent by the NRCC. (The DCCC continues to be the major player on the Democratic side.) That's turned the NRCC into the junior partner this year, and it's led to some friction between the two organizations, whose priorities have lately have diverged somewhat.

As a result, we've seen a few contests where either the CLF or the NRCC—but not both—have quit the field. It could mean they're strategically divvying up the field, or it could mean that one group has given up on the race in question and is rolling its eyes at its counterpart's refusal to face up to reality. For that reason, we're only willing to conclude that a Republican-held seat has truly been triaged if we know both groups have walked away from it—though again, there's still plenty of time for decisions like that to get reversed (something we have in fact seen in previous election cycles).

And as you scan our tracker, bear in mind that there's a "good kind" of triage, too, which we alluded to above: Sometimes parties cancel ad reservations (or never make any in the first place) because they think a seat is secure. That appears to be the case in California's 21st District, where the NRCC previously cancelled October ad time because they reportedly feel good about GOP Rep. David Valadao's chances. These are just all things to bear in mind as you—and we—keep our eyes on which races have been triaged and which are still competitive as we draw close to Election Day.