By Greg Giroux, CQ Staff

The Democratic Senatorial Campaign Committee (DSCC), which is heading the effort to increase its party’s majority in the Senate in the Nov. 4 election, spent $19 million in September on an independent expenditure campaign concentrated in Republican-held seats, according to a campaign report it filed Monday.

The DSCC’s September independent expenditures (IEs) were spread out over eight states, seven in which Republican incumbents are being vigorously challenged for re-election and one in which a GOP incumbent is retiring. Independent expenditures are the unlimited outlays for television commercials and other campaign expenses that national party committees are not allowed to coordinate with Senate candidates’ campaigns.

The DSCCs partisan counterpart, the National Republican Senatorial Committee (NRSC), spent $10.4 million last month on IEs, or a bit more than half as much as the DSCC. The NRSC’s September IE spending came almost exclusively in states in which Republicans are the defending party — underscoring the Republican Party’s defensive crouch as it tries to prevent huge Democratic gains.

IE spending comprised the majority of spending for both Senate campaign arms in September, when they spent down some of the significant cash reserves the DSCC and NRSC built up during the two-year election cycle. The DSCC raised $14.4 million in September, spent $21.8 million and began October with $26.3 million left to spend. The NRSC raised $6.6 million in September, spent $16 million and ended the month with $17.4 million cash-on-hand.

Both party committees spent more in New Hampshire last month than in any other state. The DSCC laid out $5.2 million to help Democratic former Gov. Jeanne Shaheen as she bids to unseat Republican Sen. John E. Sununu . The NRSC spent $2.4 million last month in a race that CQ Politics rates as Leans Democratic, which means Shaheen has a slight edge.

Both party committees spent money in five other states: North Carolina, where Republican Sen. Elizabeth Dole is struggling against Democratic state Sen. Kay Hagan; Mississippi, where appointed Republican Sen. Roger Wicker is in a tossup race with Democratic former Gov. Ronnie Musgrove; Colorado, where Democratic Rep. Mark Udall has a lead over Republican former Rep. Bob Schaffer in the race to succeed retiring Republican Sen. Wayne Allard ; Oregon, where Republican Sen. Gordon Smith is in a very close race with Democratic state House Speaker Jeff Merkley; and Minnesota, where Republican Sen. Norm Coleman is opposed by Democrat Al Franken and the Independence Party’s Dean Barkley.

The DSCC also spent some IE funds last month in Maine, where Republican Sen. Susan Collins leads Democratic Rep. Tom Allen , and in Alaska, where an approaching verdict in the corruption trial of Republican Sen. Ted Stevens will determine whether he can ward off Democratic challenger Mark Begich, the mayor of Anchorage. The NRSC spent some money in Louisiana, where Democratic Sen. Mary L. Landrieu leads Republican state Treasurer John Kennedy.

The Senate reports also showed a stark partisan imbalance in donations from senators, who are permitted under the federal campaign finance law to transfer as much money as they wish from their own campaign committees to the national party committees.

The DSCC received transfers from about 20 senators, including $1 million apiece from Massachusetts Sen. John Kerry , who was the 2004 Democratic presidential nominee, and Illinois Sen. Richard J. Durbin , who ranks second in the Democratic Senate hierarchy as Majority Whip. The DSCC also received a $250,000 transfer from the Senate campaign of Delaware Democrat Joseph R. Biden Jr. , the Democratic vice-presidential nominee who is expected to easily win a new Senate term he is simultaneously seeking, but may never serve.

The NRSC, by contrast, received contributions last month from just three Republican senators — including Nevada Sen. John Ensign , who has not been able to convince many Republican senators to give surplus campaign funds to his committee.

Democratic Senatorial Campaign Committee (DSCC)

• September 2008 receipts: $14.4 million

• Cycle-to-date receipts: $117.3 million