Forget the polls. Watch this one key leading indicator, and you’ll have a good idea of whether Republicans should worry about losing the House of Representatives next year.

Newly elected House Speaker Paul Ryan of Wis., receives the Speaker’s gavel from House Minority Leader Nancy Pelosi of Calif., in the House Chamber on Capitol Hill in Washington, Thursday, Oct. 29, 2015. Republicans rallied behind Ryan to elect him the House’s 54th speaker on Thursday as a splintered GOP turned to the youthful but battle-tested lawmaker to mend its self-inflicted wounds and craft a conservative message to woo voters in next year’s elections. (AP Photo/Andrew Harnik)

Normally when we predict the Congressional elections, we use polls. But the polls can be wrong, especially in this era of cheap robo polling. But there’s one clear indicator of whether it’s going to be a bad year for a party: we watch how many of them retire from politics.

Not all retirements are a bad sign: Sometimes incumbents retire to run for another office. That’s ambitious, and it’s not a bad sign. It’s a bad sign when they just quit. Just quitting means they already know they’re going to lose, so they get when the getting is good. That or they know they’re going to lose the majority, and so they quit before it stops being fun.

Only four times since the 1994 realignment has a party needed 10 or more retirements above the other party. In 1994, the Democrats had 26 retirements to 7 for the Republicans, D+19. In 2000, Republicans had 17 to 3 for the Democrats (R+14). In 2008, the GOP saw 23 retirements to 3 for the Democrats (R+20). And in 2016, the GOP had 20 retirements to 8 for the Democrats (R+12).

Four times it happened. Three times it came during a Presidential election, and the Republicans retired en mass on the way to the Democrat getting more votes than the Republican, however it just happens that the Republican squeaked by in two of those years with the Electoral Vote. It’s still a terrible sign to get out-voted in an election.

The one, the only time it happened in a midterm was 1994 itself, possibly the most devastating midterm loss a party has suffered in the modern era. Sure, Republicans gained more seats in 2010 than in 1994, but 1994 ended decades of Democrat-run majorities. It was the sign of a major partisan realignment that has lasted since.

So that’s your number to watch. If Republicans have at least 10 retiring members more than the Democrats do, excluding members running for another office, we can expect that Nancy Pelosi has a shot at being Speaker. If they hit 20, then the sky is falling. Currently that number is 6, as 7 Republicans have announced retirements to only 1 Democrat. That’s not a great start, but Paul Ryan still has hope.