The polls show the lead contenders neck and neck, and the national parties expect to spend richly on the race.
But in the fifth and final debate scheduled in Pennsylvania's Seventh Congressional District, the Republican candidate, Patrick Meehan, didn't show.
That meant that Democratic candidate Bryan Lentz aimed his sharpest attacks at a phantom. And it left Lentz alone onstage with the third-party candidate his campaign helped prop up.
Democrats and Lentz volunteers gathered thousands of signatures for Jim Schneller, an independent conservative Democrats hope will snag votes from Meehan on Nov. 2.
Meehan pulled out of the debate last week after the host of the debate, the League of Women Voters, refused to rescind its invitation to Schneller.
"Pat Meehan will not debate Bryan Lentz along with his running mate, Jim Schneller," said Virginia Davis, a spokeswoman for the Meehan campaign.
Schneller had been excluded from the previous four debates.
The League of Women Voters invites all candidates on the ballot to debate, said Marita Green, vice president of voter services for the central Delaware County branch of the organization.
"I don't have any particular feeling for Schneller or Lentz or Meehan, but if you are to try to educate the public, all of the candidates should be there," Green said. "And third-party candidates sometimes have ideas.
"It's just not right," she said of Meehan's absence.
Both candidates who did appear had choice words for Meehan.
Schneller, 54, of Wayne, said Meehan shirked his duty to Seventh District voters by ditching the debate.
"At one point, does backing out of a debate become more important that giving the electorate first preference?" he said before the debate began.
Lentz, 46, a two-term state representative from Swarthmore, called for additional debates with Meehan.
"It's just an excuse," Lentz said of Meehan's reasoning to forgo the debate. "Getting the job done means showing up and answering questions." He added, "I think he'd rather rely on television commercials than face the voters."
Some Democrats say Meehan, 54, of Drexel Hill, is terrified to share the stage with Lentz after his last debate performance. Meehan sweated heavily and stumbled through some of his responses at the debate, on Sept. 21 at the Suburban Jewish Community Center in Haverford.
That video provided rich fodder for a snarky attack ad courtesy of the Lentz camp. Some Democratic political insiders have compared the scene to the 1960 televised debate between a cool John F. Kennedy and a sweating Richard M. Nixon. The Meehan campaign has called that claim "ridiculous."
Attendance at Thursday's debate was sparse. About two dozen people attended the event at Delaware County Community College's Marple campus.
Among the issues discussed by Lentz and Schneller were taxes and the war in Afghanistan.
When asked whether he would support extending the Bush tax cuts, Schneller blanked out in the middle of his answer.
"Taxes disturb me so much, I automatically go into overdrive," he said. He added that taxes were an undue and increasing burden, and recommended reforming the tax code.
Lentz has said he would repeal only the tax cuts to those who make more than $250,000 a year. Meehan supports keeping all of the tax cuts.
On Afghanistan, Schneller's answer was simple: Get out. He said the wars in Iraq and Afghanistan have been a "moneymaking scheme" for vendors like Halliburton.
Lentz, a former Army Ranger who was deployed to Iraq in 2004, called for a timetable for exiting Afghanistan, a measure Meehan does not support.
"The long-term accomplishments in Afghanistan are limited, they are modest," he said. "And they are not worth $100 billion a year and . . . countless lives."
"Pat Meehan," he added, "favors a war without end."
Meehan, who worked as Delaware County's district attorney before becoming U.S. attorney, has an edge on Lentz with name recognition in the heart of the Seventh District, which includes Delaware County and parts of Montgomery and Chester Counties. But recent polls, including one released Thursday by Franklin and Marshall College, show Meehan leading Lentz by a hair at most.
Schneller, according to the latest poll, is pulling about 2 percent of the vote, and many voters surveyed said they remained undecided.