Illinois state Sen. Barack Obama (D) has become an increasingly generous benefactor to the Democratic effort to take back the Senate — a move that puts him in good standing with his would-be colleagues in the chamber and at risk for some criticism back home.

Obama, a rising Democratic star who is all but guaranteed to win the Illinois Senate race next month, has been more aggressive in fundraising and traveling for other candidates since delivering the keynote address at the Democratic National Convention in July. In the latter part of September, Obama raised and contributed a total of more than $500,000 to Democratic candidates and causes.

Last week alone, Obama cut checks for $100,000 to the Democratic Senatorial Campaign Committee as well as $25,000 each to the state parties in Colorado, Wisconsin, Alaska, South Dakota and Oklahoma — all of which are hosting top-tier Senate battles. He also gave $25,000 to Florida Victory 2004, a fund set up to aid the Senate bid of former state Education Commissioner Betty Castor (D).

In addition, last month Obama raised $260,000 in individual contributions from his campaign donors for Senate candidates in 13 states. That figure includes $53,000 he raised for Senate Minority Leader Tom Daschle (D-S.D.), who is facing a tough challenge from former Rep. John Thune (R).

Obama raised lesser amounts for open-seat Democratic candidates such as North Carolina investment banker Erskine Bowles, Rep. Brad Carson (Okla.), former Alaska Gov. Tony Knowles, Colorado Attorney General Ken Salazar and South Carolina Superintendent of Education Inez Tenenbaum.

Those direct contributions to candidates and state parties are in addition to the $850,000 Obama’s campaign estimates he has raised for the DSCC, either in call time to donors or joint fundraisers, since winning the Senate nomination in March.

“Barack Obama believes that he has as opportunity to help out other Democratic candidates throughout the country and believes that that will strengthen his position and the argument he makes on behalf of Illinois when he gets to the Senate,” said Obama spokesman Robert Gibbs.

He also headlined a fundraiser last month for House candidate Melissa Bean, who is challenging veteran Rep. Phil Crane (R-Ill.), that raised $75,000.

It is virtually unprecedented for any nonincumbent to be able to funnel resources to national party causes, instead of vice-versa.

But Obama is expected to cruise to victory Nov. 2 over two-time failed presidential candidate Alan Keyes (R), who is running a shrill campaign. The most recent polling in the race showed Obama led Keyes 69 percent to 24 percent. He would become the third black elected to the Senate since Reconstruction.

Through June, Obama had raised almost $10 million for his own effort. Campaign aides could not say Wednesday how much he had raised through the end of September, but clearly it is more than he feels he needs.

“We could not be more grateful for the support Barack Obama has given to the DSCC and to our candidates,” said Sen. Jon Corzine (N.J.), the committee’s chairman. “It’s unprecedented and historic to receive this level of support from someone who has yet to be elected to the Senate and it is a testament to Barack’s sincere desire to elect a Democratic Senate Majority. When it comes to his support of our effort to retake the Senate, Barack Obama deserves a gold medal.”

The young, Harvard-educated attorney has become a sought-after commodity on the campaign trail. Last month he visited Pennsylvania to stump for Rep. Joe Hoeffel (D), as well as other Senate candidates.

He also further fueled talk of a possible future presidential run when he visited Davenport, Iowa, on Monday to raise funds for the state House and Senate Democratic caucuses.

Obama is scheduled to make several more appearances on behalf of Democrats this month, including several rallies for the presidential ticket of Sens. John Kerry (Mass.) and John Edwards (N.C.).

This weekend he will appear in Milwaukee with Sen. Russ Feingold (Wis.) and other Democratic candidates.The following Friday, Obama will be in Los Angeles for a DSCC fundraiser that is expected to net $1 million for the party. Before that, he will attend a Las Vegas rally for the Democratic ticket. Then on Oct. 16 he will visit Colorado to stump for Salazar, the state attorney general, and Kerry.

Republicans in Illinois say Obama is already forgetting the voters back home.

“While Obama continues to bask in his new-found national stardom, it’s the voters of Illinois who are going to decide who the next Senator from Illinois is going to be — not South Dakota, not Pennsylvania and not Iowa,” said Jason Gerwig, spokesman for the Illinois Republican Party.

Dan Proft, Keyes’ deputy campaign manager, acknowledged that Obama has been able to raise a large amount of money because he has become a “deified figure” and a “darling of the extreme liberal left.”

“Someone should remind Barack that he’s won exactly the same number of federal elections as Alan Keyes has, and that number is zero,” Proft said.

Obama and Keyes are scheduled to meet for three debates this month.

“Illinois voters are going to have a clear choice after those debates and as they start focusing in on this important race in Illinois,” Proft said.

Still, Obama’s generosity has not gone unnoticed — and it is not likely to go unrewarded — within the caucus of his would-be peers.

“Barack Obama has collected a lot of chips from his future Senate colleagues by so actively campaigning and raising money for them and the DSCC,” said one Democratic operative. “Barack Obama’s going to be able to cash in big time for his constituents when he gets to Washington. His efforts are going to put him in good stead with his future colleagues.”