Rep. Mark Kirk (R-Ill.) announced Monday that he raised more than $1.6 million during the third quarter, his first full quarter as a Senate candidate, more than doubling his second-quarter fundraising haul. Known for his prolific fundraising abilities, Kirk’s relatively low $590,000 second-quarter total raised eyebrows among some in his own party. The North Shore Chicago Congressman was publicly mulling a bid for Senate during the second quarter and officially jumped in the race in mid-July. Kirk’s campaign said he raised $1.5 million after he announced his bid July 20. He ended September with a total of $2.3 million in cash on hand. An aide for state Treasurer Alexi Giannoulias, the frontrunner in the Democratic primary, said the campaign was not ready to release its third-quarter fundraising totals yet. Giannoulias announced at the end of June, however, that he had almost $1.7 million in the bank. The other Democrats in the race, former Chicago Urban League President Cheryle Robinson Jackson and former Chicago Inspector General David Hoffman, officially started to fundraise last month and have not released their totals so far. Kirk has several minor primary challengers, including real estate developer Patrick Hughes.