LANGHORNE, Pa. — Steve Santarsiero stood in front of about a dozen supporters, many of whom had slipped on green T-shirts over their sweatshirts or long-sleeved flannels. This was a group, the Democratic House candidate figured, who already understood the importance of his race.

“I’m not going to talk about the overall landscape this year,” he said, speaking inside his small campaign office on a crisp Saturday morning. “I think we’ve discussed it at length, and everybody in this room knows what’s at stake.”

Santarsiero, a state representative, is running in Pennsylvania’s 8th Congressional District, an open-seat race in suburban Philadelphia that House Democrats consider a top target. The district is middle-class and ideologically moderate — the kind that, in a wave election for Democrats, should easily turn blue. 

The question is: Is this a wave election? A week before Election Day, everyone is trying to find an answer.

The members of the Sierra Club who had gathered, dressed in their trademark green, certainly hope there is a wave. So do officials from the Democratic Congressional Campaign Committee, some of whom drove from Washington to Bucks County that morning to help out their candidate. Both groups would fan out across the district Saturday to knock on doors and talk with voters, urging them to back the Democrat.

But evidence of a wave — both in Bucks County and across the country — appears only in fits and starts. Democrats have reason for optimism: In many polls, Hillary Clinton is on track to defeat her GOP presidential rival Donald Trump by a larger margin than President Barack Obama did against Mitt Romney four years ago, and a plethora of competitive House seats have tilted toward the Democrats in recent weeks.

The National Republican Congressional Committee has had to spend big and late in unexpected places, like Indiana’s 9th District, the kind of behavior that suggests the broader climate has taken a turn for the worst.

And yet, the shock revelation last week that the FBI will review potentially new emails possibly related to its investigation of Clinton’s private email server could cut into her lead.

Left-leaning seats the party once expected to win handily have also instead proved difficult, a dynamic at work even in Senate races. Last week, a Democratic super PAC had to make a surprise last-minute investment in the Wisconsin Senate race, a contest the party had long considered a sure victory.

And in Santarsiero’s race, Democrats have encountered fierce resistance. The state lawmaker trails Republican Brian Fitzpatrick, a former FBI agent, in a contest where Democrats believe they have momentum but concede that victory is far from guaranteed — or even likely.

“They’re banking on a wave here, and they’re going to be sorely disappointed,” Fitzpatrick said. “Because it’s not going to happen.”

Why not a wave?

Democrats need a Clinton blowout to facilitate a down-ballot wave. But every time she appears on the verge of breaking away from Trump, her numbers fall back to earth.

Republican strategists say fallout from three events had them holding their breath about the damage it would do: Trump’s racial criticism of federal judge Gonzalo Curiel, the case against Trump made at the Democratic National Convention, and the videotaped 2005 remarks of Trump bragging about groping women.

The “Access Hollywood” video, in particular, sent the party into a tailspin in early October, according to GOP strategists. At the time, they worried Democrats were on track to win a majority in the Senate (and then some) while making big gains in the House.

But as has happened throughout the campaign, the presidential race tightened just as Clinton appeared set to run away with it. A Washington Post-ABC News tracking poll shows her once comfortable lead has shrunk to just one point as of Monday.

For all of Trump’s controversies, the country’s polarized electorate makes it hard for any candidate to break out, say Democratic strategists.

“The partisanship of this country is such that blowouts are no longer a likely reality,” said Jefrey Pollock, a top Democratic pollster. “Even in situations where it looks like it could be.”

Pollock said that, unlike public polls, the party’s internal polls have shown very little movement in the presidential race over the last month, especially in swing states.

Republicans have a different explanation: Clinton’s own unpopularity. The Democratic nominee is nearly as unpopular as Trump overall, polls show, and even less popular among some key demographics.

“Clearly Donald Trump has caused Republicans a lot of problems among women,” said a senior GOP strategist. “But Hillary Clinton is having her own problems with men, making it harder for Democrats down ballot.” (Another Republican strategist quipped that if Vice President Joseph R. Biden Jr. were the Democrats’ nominee, the House GOP would be in “severe trouble.”)

A Clinton victory by 5 or 6 points could still put congressional GOP candidates in a tight spot. That’s especially true in suburban districts with a high share of well-educated white voters and minorities.  

Republicans, for instance, are nervous they could lose as many as four seats in California, driven in part by fear that an early Election Night call for Clinton could depress GOP turnout on the west coast.

“I think there’s a lot more energy on the Democratic side,” Santarsiero said. “I can tell you, based on the past, in 2008, there was the same kind of energy among activists and supporters that we’re feeling right now. So that’s certainly a good sign for the Democratic ticket.”

Individual factors

Brian Fitzpatrick is a new candidate in the 8th District. But as he walked up and down this small borough’s harvest festival — which featured calorie-heavy donut stands and re-enactors of both the Revolutionary and Civil wars — voters walked up and greeted him like an old friend.

Fitzpatrick has an unusual advantage in this race: His brother, Michael G. Fitzpatrick, is the incumbent congressman. Operatives from both parties acknowledge that, at first, voters likely saw that a “Fitzpatrick” was running and assumed the popular incumbent was running for re-election.

They know the difference between the two men now — thanks in part to an aggressive ad campaign from the DCCC that explicitly says Brian is a different person than his brother —but the family bond still seems to work in Brian Fitzpatrick’s favor.

“I’ve spend enough time with Mike to appreciate you taking over his seat,” one man told Fitzpatrick as he shook his hand at the festival.

The 8th District seat has changed partisan hands in recent wave elections. Michael G. Fitzpatrick lost the seat in 2006 to Democrat Patrick J. Murphy amid that year’s blue wave. Four years later, during the GOP’s wave election of 2010, he won it back from Murphy.

But as is the case elsewhere, factors in these individual House races matter, too. Democrats say they’ve been impeded by the high number of Republican incumbents in many of these races.

It explains, according to Pollock, why the party has struggled to put away seats it expects to win even as it expands the numbers of pickup opportunities in less favorable districts.

“A traditional wave, that means an overwhelming number of House seats go your way, and I think that has always been hard,” the pollster said. “It’s hard because of redistricting, it’s harder because of partisanship, with individuals that have become far more polarized.”