The National Republican Senatorial Committee out-raised its Democratic counterpart during the month of May by about $1 million — with $4.5 million in receipts to the Democratic Senatorial Campaign Committee’s almost $3.5 million.

The NRSC’s total includes a $1 million transfer that the Republican National Committee made to the NRSC during the month, but even without the financial assist, the GOP committee still had a slightly better May than the Democrats did.

According to numbers set to be reported to the Federal Election Commission, the DSCC has a slight cash-on-hand lead with $4 million to the NRSC’s $3.7 million.

But the NRSC was able to pay off its remaining debt from the 2008 cycle in April while the DSCC was $4.2 million in the hole as of May 31.

Five months into the 2010 cycle the DSCC and NRSC are nearly equal in total fundraising, with the Democratic committee having brought in almost $17 million in total receipts and the Republican committee having raised $17.2 million.

Both committees held major fundraising dinners this month featuring high-profile party leaders, and it will be interesting to see if the fundraising parity continues in June.