Massachusetts Republican Richard Tisei raised nearly $435,000 in the last quarter of 2013 for his rematch with Rep. John Tierney (D-Mass.).
And, in the week since officially announcing his bid, Tisei raised an additional $100,000 for the first quarter of this year.
The strong showing puts him on solid financial footing for the rematch, which is expected to be a tough battle.
Tierney won in 2012 by 1 percentage point, and Republicans believe a less-favorable political atmosphere without Obama at the top of the ticket, coupled with persistent issues with ObamaCare, could deliver them a win this time around.