AUGUSTA — Independent Angus King continued to lead his rivals for Maine’s open U.S. Senate race in fundraising over the past three months, according to fundraising figures from the latest reporting period released by the candidates’ campaigns.

Meanwhile, Republican Charlie Summers accelerated the pace of his fundraising during the past quarter while Democrat Cynthia Dill fell even further behind her two opponents in the funds race. Dill added less to her Senate campaign account between July 1 and Sept. 30 than she did in the previous quarter.

Third-quarter campaign finance reports were due to federal election officials Monday. Dill’s campaign released its full report Sunday while the campaigns for Summers and King released aggregate fundraising numbers Friday and Monday, respectively.

King added more than $1.1 million to his fundraising total between July 1 and Sept. 30, according to figures released by his campaign. That brings the former governor’s fundraising total since he entered the race in March to nearly $2.1 million.

King’s campaign had $464,000 left to spend as of Sept. 30, compared to $503,000 he had on hand at the end of June. The campaign said 53 percent of its total contributions have come from within Maine.

Summers raised $507,000 in July, August and September, his campaign said. That brings his total fundraising to about $746,000 since he entered the Senate race in March. The third-quarter number is double the amount Summers had raised through June 30.

Summers had $189,000 left to spend as of Sept. 30, compared to $119,000 on hand three months earlier. His campaign said half of all third-quarter contributions were $200 or less.

According to Dill’s campaign finance report, the state Senator from Cape Elizabeth raised $57,000 during the third quarter — compared to $66,000 between April 1 and June 30 — and spent $76,000. The $57,000 figure brings Dill’s total fundraising for the Senate race to $148,000.

She ended the third quarter with $10,000 left on hand, compared to $28,000 on June 30.

While candidate fundraising picked up over the past quarter, it lags behind the $4.4 million outside groups have spent so far on ads designed to bolster Summers’ and King’s candidacies.

According to expenditure reports filed with the Federal Election Commission, Republican groups have spent $2.8 million since the end of July almost entirely on ads attacking King. The latest was a $500,000 anti-King ad campaign from the U.S. Chamber of Commerce, which has endorsed Summers.

Spending on ads designed to benefit King, however, has started to catch up. The Democratic Senatorial Campaign Committee — which hasn’t endorsed Democratic nominee Dill — has spent $700,000 so far on ads attacking Summers while the nonprofit organization Americans Elect has spent almost $900,000 on television advertising and direct mail on King’s behalf.