Altschuler, a St. James businessman, raised more money than Bishop for the second straight quarter, $306,829 to $258,941. Bishop retains a cash-on-hand advantage, with $1.24 million as of March 31 compared with Altschuler's $775,357.
But that lead is down by nearly $75,000 since January.
"We feel very good about continuing to close that gap before the campaign gets to the fall," said Altschuler consultant Chris Russell. "Especially given our advantage with individual donors."
Individuals accounted for more than 90 percent of Altschuler's contributions this past quarter; they were about 46 percent for Bishop. But Bishop spokesman Oliver Longwell said Altschuler relies heavily on out-of-district donors, while Bishop claims more local support.
Altschuler's "donor base of millionaires calculates they will get a good rate of return by helping him buy Eastern Suffolk's congressional seat," Longwell said, also noting that Bishop's cash-on-hand lead is more substantial when the Altschuler committee's debt is considered.
The race for New York's 1st Congressional District is expected to again be close. Altschuler lost to Bishop by 593 votes in 2010, when he did not have the Independence Party endorsement he received earlier this year.
Recent polling by Bishop's campaign show the incumbent with a sizable lead so far in this fall's race. Altschuler aides dismiss the findings as "desperate attempts" to depress the challenger's fundraising.