Republican Senators have collected or given some $4.4 million to their party committee so far this cycle, but the bulk of the fundraising rests with just a few of the Republican Conference’s top leaders, according to an internal party document obtained by Roll Call.

The National Republican Senatorial Committee laid out its latest fundraising data in a detailed spreadsheet it delivered this week to Senators. Titled “NRSC Senate Fundraising Tracking,” the memo outlines how much each Senator has raised, given and committed to the committee as well as how much Senators have given directly to GOP candidates and the number of fundraisers they’ve attended through May 15.

Not surprisingly, NRSC Chairman John Ensign (Nev.) leads the pack with steering a total of $994,000 to the Senate fundraising arm to date. That figure represents the money Ensign has given from his leadership political action committee to the NRSC as well as the amount he’s raised on behalf of the NRSC. On top of that, Ensign has given $65,000 directly to GOP candidates from his PAC.

Other Republican leaders also are among the more prolific Senate Republican givers. So far, Minority Leader Mitch McConnell (Ky.) has raised and given $575,000 to the NRSC and $150,000 directly to GOP candidates, followed by Minority Whip Trent Lott (Miss.) who has raised and given $175,000 to the NRSC and $61,000 to candidates, and Republican National Committee General Chairman Mel Martinez (Fla.), who has raised and given $220,000 to the party fundraising arm.

Rank-and-file Republicans making a strong showing include Sen. Kit Bond (Mo.), who has raised and given $160,000 to the NRSC and shelled out $17,500 directly to candidates; Sen. James Inhofe (Okla.), who has steered $216,000 to the committee; Sen. Johnny Isakson (Ga.), who has given $222,500 to the NRSC and another $21,000 to candidates; and freshman Sen. Bob Corker (Tenn.), who has raised $234,000 on behalf of the NRSC.

Questioned about the document in a brief interview Wednesday, Ensign acknowledged that “some” of his colleagues are heeding the pressure to meet the ambitious fundraising goals he set earlier this year. But Ensign was quick to add, “We need to continue to do a better job.”

Asked whether there are specific areas of fundraising that need improvement, the Nevada Republican responded: “Yeah, raising money.”

Ensign set a goal to raise $119 million over the two-year period, the same amount collected in the 2006 cycle by his counterpart Sen. Charles Schumer (N.Y.) at the Democratic Senatorial Campaign Committee. In the first quarter of 2007, the NRSC collected $7 million, about half of what the DSCC raised over the same time period.

Some Republican Senators are doing more than others. According to the NRSC document, direct leadership PAC contributions to GOP Senate candidates are just more than $1.1 million so far.

Excluding those Senators who are retiring or up for re-election in 2008, the most frugal Senators include presidential hopefuls John McCain (Ariz.) and Sam Brownback (Kan.) as well as Sens. Jim Bunning (Ky.) and Lisa Murkowski (Alaska), all of whom have failed to register a dime for the committee or GOP candidates, according to the NRSC tally.

Overall, 19 of the 49 GOP Senators have given from their leadership PACs to the NRSC, largely in $15,000 increments, or the maximum allowed annually under campaign finance laws. Beyond that, 22 Senators have tapped into their leadership accounts to give directly to Republican Senate candidates this cycle.

Attending the most NRSC events so far this cycle are Ensign with 11, Sens. Norm Coleman (Minn.), one of the GOP’s most vulnerable incumbents, with nine, Saxby Chambliss (Ga.) with eight, Corker with seven, and Inhofe, Bond and Jim DeMint (S.C.) with six fundraisers apiece.