More than half of the challengers in races Roll Call categorized as tossups out-raised their incumbent opponents in the third quarter, the last quarter before Election Day, Nov. 6, the Washington publication said.
The review did not include member-on-member races or open-seat battles.
Ami Bera, a Democratic physician from California, and Richard Tisei, a Republican and one-time Massachusetts state senator, were among those who raised significantly more money than their incumbent foes. In both tilts, the veteran congressmen are considered slight underdogs.
Bera, who lost to Rep. Dan Lungren, R-Calif., by about 7 percentage points in 2010, raised $747,000, financial reports indicated. Lungren collected $516,000.
Tisei, the GOP nominee for lieutenant governor in the Bay State in 2010, amassed $661,000 in the third quarter, while eight-term Rep. John Tierney, D-Mass., raised $508,000.
In two New Hampshire congressional races that are repeats of 2010 matchups, Democrats Carol Shea-Porter and Ann McLane Kuster out-raised their Republican opponents, Reps. Frank Guinta and Charles Bass, Roll Call said.
Other tossup races, as determined by Roll Call, in which the challenger out-raised the incumbent include:
-- California's 9th Congressional District, where Republican Ricky Gill out-raised incumbent Jerry McNerney.
-- Illinois' 11th Congressional District, where Democrat Bill Foster raised more money Rep. Judy Biggert.
-- New York's 18th Congressional District, where Democrat Sean Patrick Maloney bettered freshman Rep. Nan Hayworth.
-- Pennsylvania's 12th Congressional District, where Republican Keith Rothfus raised more funds than Rep. Mark Critz.
-- Utah's 4th Congressional District, where Republican Mia Love collected more money than Rep. Jim Matheson.
Notable deaths of 2014 [PHOTOS]