Scores of candidates were announcing their intentions in terrain recently considered inhospitable to Democrats: West Virginia, Texas, Kansas. Some aspirants Russell met lacked the talent to match their enthusiasm. Others were hot property and elected to go with one of Beacon Media’s competitors. But by Labor Day, Russell and his firm had picked up 10 Democratic challengers. Among them were a few beguiling dark horses, like a 46-year-old physician and former Y.M.C.A. national health officer from Portage, Mich., named Matt Longjohn. Undeterred by his lack of political experience, Longjohn was challenging Fred Upton, a Republican who had represented Michigan’s Sixth District for three decades.

Russell himself grew up in the Sixth District and cast his first ballot as a registered voter against Upton in 2002. Back then, the incumbent seemed invincible. But now, after leading the committee that wrote the legislation seeking to eviscerate Obamacare, Upton was avoiding town halls and any other public events.

Still, when I met Russell recently, his optimism was tempered by previous electoral disappointments. The Democratic Party now has more candidates than it can support, and next spring is likely to be a season of what national Democratic officials tactfully refer to as “messy primaries.” And even with Trump as a foil, Russell’s candidates were struggling to make a case for themselves. “Right now it’s such a target-rich environment for us,” he told me. But “we’re having trouble explaining why we’re the heroes and the Republicans are the villains. At some point, our narrative will have to become more coherent than it is now.”

In pursuit of the 24 seats Democrats need to win the House, the D.C.C.C. intends to target 80 Republican-held districts — a dozen more than the party went after in its 2006 bonanza year, when it captured a majority after gaining 31 seats. Many of next year’s seem to be fanciful propositions, or strategic plays designed to force the G.O.P. to spend resources where it would rather not. In other cases, the D.C.C.C. is counting districts held by controversial Republicans — Chris Collins of New York, with his aggressive advocacy of a biotech firm in which he held substantial investments; Duncan D. Hunter of California, with the possibility of a federal indictment for supposed campaign fund malfeasances hanging over his head — who nonetheless appear safe, at least for the moment. But four Republican representatives in potential swing districts — Ileana Ros-Lehtinen, Dave Reichert, Charlie Dent and Pat Tiberi — have already announced their retirement in advance of 2018, and more are expected to follow before the end of the year.

Only two times in the last century (during the Great Depression and after the Sept. 11 attacks) has a president’s party not suffered electoral losses midway into his first term. Those losses — an average of 32 House seats in each such midterm since 1862 — increase to 36 when the president’s approval rating is under 50. President Trump’s polling average has never once exceeded a favorability rating of 48 percent, and it now hovers at about 37 percent.

“I think the best thing the Democrats can do,” Zac Petkanas, formerly the director of rapid response for the Clinton campaign, told me, “is find as many people with a pulse, with a D next to their names, in as many districts as possible, and run on Obamacare and standing up to Trump.” But so much of the politics, and political mood, of Trump’s presidency is off the map of previous experience that other Democrats have seemed at times at a loss for how to respond. What to make of the late August NBC poll, for instance, that showed Democrats being viewed unfavorably by 54 percent of those surveyed, which was better than Republicans (61) and Trump (61), but also Pelosi (64)? Was that good news or bad news? And what about the D.C.C.C. focus groups and polls yielding the conclusion that voters broadly dislike Trump but are also put off by candidates who profess to be “standing up to Trump,” on the grounds that such resistance will only guarantee more dysfunction in Washington?

Republicans are hopeful that, Trump being the exception to almost every political rule, the historical trends of wave elections will also not apply to him. “Clinton came up against a wave in 1994 because he had campaigned as a centrist but then led with gays in the military and Hillarycare,” Karl Rove, the former senior adviser to President George W. Bush, told me. “The 2006 election was a wave because Republicans were defending the Iraq war and crippled by a late-breaking ethics scandal. Democrats faced a wave in 2010 because of Obamacare. So it’s been issues that have driven wave elections. This time around, I think it’s more a personal antagonism to Trump. And the question is, how critical will that be in shaping the attitudes of swing voters?”