The Blue Wave that wiped out the Repub­li­can House major­i­ty brought a num­ber of sur­pris­es in heav­i­ly GOP dis­tricts: Kendra Horn now holds a seat in deep-red Okla­homa, and Joe Cun­ning­ham pulled through in South Car­oli­na. But even as Democ­rats seemed to win House races every­where, many can­di­dates upon whom pro­gres­sive orga­ni­za­tions staked big bets came up short. Randy Bryce (Wis.), Jess King (Pa.), Liu­ba Grechen Shirley (N.Y.), Ammar Cam­pa-Naj­jar (Calif.) and Leslie Cock­burn (Va.), all con­test­ing red seats and endorsed by insur­gent pro­gres­sive groups, lost. One rea­son is sim­ple: They were in tougher-than-aver­age dis­tricts. But the oth­er prob­lem is strate­gic: Back­ing bomb-throw­ers in pur­ple and red dis­tricts is not how to pull the par­ty left.

Progressive organizations simply don’t have enough money, media or organizers to aggressively contest primaries in both blue and purple districts.

One the­o­ry of change guid­ing some cam­paigns this cycle has been that an unapolo­getic left plat­form could boost turnout and win over work­ing-class vot­ers in Repub­li­can areas where Bernie Sanders per­formed well in the 2016 Demo­c­ra­t­ic pri­ma­ry. The prob­lem, of course, is that Bernie was run­ning in the Demo­c­ra­t­ic pri­ma­ry — his suc­cess doesn’t tell us what gen­er­al elec­tion vot­ers want in these dis­tricts. This is not to say that a Medicare-for-All can­di­date can­not win, sim­ply that Demo­c­ra­t­ic pri­maries offer the best hope to get insur­gent can­di­dates in office and pull the par­ty left.

To see why, mere­ly count the unabashed pro­gres­sives who won pri­ma­ry chal­lenges in safe Demo­c­ra­t­ic dis­tricts, then sailed to vic­to­ry in the gen­er­al elec­tion: Alexan­dria Oca­sio-Cortez (N.Y.), Deb Haa­land (N.M.), Chuy Gar­cia (Ill.), Rashi­da Tlaib (Mich.), Jahana Hayes (Conn.), Joe Neguse (Colo.), Ayan­na Press­ley (Mass.), Ilhan Omar (Minn.). Only one retir­ing Demo­c­rat, Rep. Collen Hanabusa (Hawai’i), was replaced by some­one who is like­ly to be to their right. Mean­while, no pro­gres­sive who unseat­ed a Demo­c­ra­t­ic con­gres­sion­al incum­bent in the pri­ma­ry went on to lose the gen­er­al election.

Look also, for instance, at how Oca­sio-Cortez has already shift­ed the con­ver­sa­tion around a Green New Deal, which an increas­ing num­ber of Democ­rats have now embraced. Run left can­di­dates to seize the safe blue dis­tricts, and the main­stream of the par­ty will follow.

It’s tempt­ing to shrug off the ques­tion of pur­ple dis­tricts ver­sus blue dis­tricts with a dis­mis­sive, ​“Why not both?” But pro­gres­sive orga­ni­za­tions sim­ply don’t have enough mon­ey, media or orga­niz­ers to aggres­sive­ly con­test pri­maries in both blue and pur­ple dis­tricts. This will be even hard­er in 2020, when the pres­i­den­tial elec­tion is sure to dis­tract from down-bal­lot races.

Sup­port for these blue-dis­trict insur­gents will come from unex­pect­ed places. Among the Left, there has been some dis­mis­sive­ness toward the anti-Trump Resis­tance, as rep­re­sent­ed by groups such as Indi­vis­i­ble and Swing Left; many have paint­ed them as cen­trists averse to chal­leng­ing Democrats.

This myth (often root­ed in misog­y­ny — the Resis­tance is pre­dom­i­nant­ly women) does not find sup­port in research con­duct­ed by Data for Progress, the think tank I co-found­ed. We found that Democ­rats with favor­able views toward Indi­vis­i­ble, com­pared to Democ­rats as a whole, are more sup­port­ive of con­test­ed pri­maries. This find­ing makes sense: These groups are full of engaged vot­ers who vote in pri­maries and are sym­pa­thet­ic to the idea that Demo­c­ra­t­ic lead­er­ship should be doing more to take on Trump.

A glance at the Indi­vis­i­ble endorse­ments points to an orga­ni­za­tion unafraid to sup­port anti-estab­lish­ment can­di­dates. In New York, six state sen­ate pri­maries were led by Indi­vis­i­ble and oth­er Resis­tance groups. Indi­vis­i­ble led an upset by a grass­roots favorite, Dana Bal­ter, over the favored can­di­date of the estab­lish­ment-friend­ly Demo­c­ra­t­ic Con­gres­sion­al Cam­paign Com­mit­tee, the House Democ­rats’ fundrais­ing arm. While many pro­gres­sive orga­ni­za­tions strug­gle to have a gen­uine local pres­ence (and increas­ing­ly strug­gle for mon­ey), Resis­tance groups could be an impor­tant base for pri­ma­ry challengers.

Although many pro­gres­sive cam­paigns lost in swing dis­tricts, there is no rea­son why red-to-blue can­di­dates can’t sup­port Medicare for All. One recent poll of five swing dis­tricts found that sin­gle-pay­er health­care had net pos­i­tive sup­port in all of them. As pro­gres­sives gain elec­toral pow­er in deep blue dis­tricts, they’ll be pulling the par­ty toward pub­lic opin­ion, not away from it.

Most red-to-blue Democ­rats, those who flipped Repub­li­can House seats, sup­port­ed some guar­an­tee of uni­ver­sal health­care, a pub­lic option, or even Medicare for All, like Sean Cas­ten (Ill.), Susan Wild (Pa.), Josh Hard­er (Calif.), Katie Porter (Calif.) and Haley Stevens (Mich.), all of whom won in sub­ur­ban swing dis­tricts. Four years ago, only one of these five dis­tricts had a pro-sin­gle-pay­er Demo­c­ra­t­ic can­di­date in the gen­er­al elec­tion. They weren’t the insur­gents that many on the Left were most excit­ed about, but their plat­forms show that insur­gent ideas are gain­ing ground.

To keep the par­ty mov­ing left and advance pro­gres­sive poli­cies, we need a sol­id back­bone of at least three dozen left pro­gres­sives in the House to hold the line. That means in 2020 run­ning pri­ma­ry chal­lenges in safe Demo­c­ra­t­ic seats with a slate of young, diverse pro­gres­sive candidates.