WASHINGTON — Jon Ossoff, the Democrat running in a closely watched special House election in Georgia, raised over $15 million in the last two months, vastly exceeding his Republican rival and shattering fund-raising records, according to federal campaign finance documents filed on Thursday.

Karen Handel, the Republican candidate for the suburban Atlanta district seat, raised approximately $4 million in the same period. But she began the final stretch before the June 20 runoff election with slightly more cash available than Mr. Ossoff, who had already spent much of his money to reserve television advertising time.

The contest to fill the seat vacated by Tom Price, the secretary of health and human services, was already the most expensive House race in history. Mr. Ossoff has now raised over $23 million and Ms. Handel, who only became the Republican nominee after the initial balloting in April, has brought in over $4.2 million. In a sign of the intense national interest in the race, much of the money came from outside Georgia.