Their cash is being drawn from divergent sources.
For Altschuler, a St. James businessman, a newer influx of super PAC money has helped supplement what had been a reliable pool of donations from Manhattan financiers.
Super PACs are political action committees allowed to spend unlimited amounts of money on campaigning, provided they operate independent of the candidates.
Bishop has found more individual donors from within his eastern Suffolk County district, and received a far larger amount of direct PAC support, largely from organized labor.
Campaign totals through June -- Bishop had raised $1.85 million to Altschuler's $1.83 million; Bishop spent $600,542 to Altschuler's $677,880 -- reflect the race's competitive nature.
And the newer $294,293 pro-Altschuler super PAC ad buy reflects the likely start of significant outside money impact, experts say, as both national parties have made electing their candidate a top priority.
"This is a race that snuck up on people last time," said Michael Malbin, a state University at Albany professor and director of the Campaign Finance Institute. "This time, everybody's looking, so you'd imagine a lot of people would want to get involved."
Altschuler had $798,816 on hand through his last disclosure. The super PAC expenditures in his name, though independent of that total, effectively add to the available money to be spent in his name.
Billionaire funds ad buys
Prosperity First Inc., which made the outside ad buys early this month, is largely funded by billionaire hedge fund manager Robert Mercer of East Setauket. The co-chief executive of Renaissance Technologies gave the group $500,000 in April, after already making the $5,000 maximum individual donation directly to Altschuler.
Bishop, as of Friday, had yet to receive super PAC money, though his backers expect at least some of that support before Election Day. At the end of June, his direct campaign had $1.5 million on hand to spend.
In 2010, when Bishop defeated Altschuler by just 593 votes -- it was the nation's last-decided House seat -- he benefited from roughly 40 percent of the $1.1 million in the race's total independent expenditures.
Take super PACs out of the equation, and Bishop and Altschuler are repeating many of the fundraising patterns of their last faceoff, according to their latest filings.
As of June 30, Bishop was getting far more in contributions from district residents than Altschuler. He received about 61 percent of his individual donations from eastern Suffolk in this year's first six months, while his challenger was getting about 31 percent, relying more on larger checks from financial industry leaders.
Bishop was also outpacing Altschuler in direct PAC contributions ($753,033, or 41 percent of his total, to $167,501). Most of that comes from labor unions giving $10,000 or more. Altschuler's biggest direct PAC supporters are those set up by Republican House members.
The candidates' next financial filings come on Oct. 15.
Both party committees, speaking last week, said they see independent spending as a factor in the race, but couldn't yet predict to what degree.
"I would hope that outside groups that want to protect Medicare instead of millionaires will monitor developments in the district," said Rep. Steve Israel (D-Dix Hills), chairman of the Democratic Congressional Campaign Committee, which raises money for the party's House candidates.
The National Republican Congressional Committee, which raises money for its House candidates, has already reserved $540,000 in television time for Altschuler, said a committee spokesman, Nat Sillin.
"We're committed to ensuring the resources are there," he said. "We view this race as one of our top pickup opportunities in the Northeast."
The candidates say they won't let outside money change their game plans.
Bishop spokesman Robert Pierce said the recent Prosperity First expenditure confirms what they've always known.
"We've done our best to keep pace," he said, "but nobody on this campaign has ever had any illusion that we were not going to be outspent."
Altschuler spokesman Chris Russell said super PAC money should flow "on both sides," but can see why his candidate may generate more support. "When people see a chance to knock off incumbents, they gravitate toward them."