Sen John Thune is weighing whether to give up his job as Republican Conference chairman to run for another leadership post, which could trigger a scramble among ambitious GOP Senators for the spots that open up.
Cornyn has also raised $100 million for the NRSC over the same period.
Cornynís early start gives him a leg up on any challengers, GOP sources said. And he could benefit from any gains the party makes in the Senate in November, particularly if he helps win the majority.
While Cornyn has been seeking the Senate GOP No. 2 spot, the top Senate Republican, Minority Leader Mitch McConnell (Ky.), has raised at least $3 million to help his party win the majority in the past two years. He has traveled across the nation working to help Senate candidates raise funds, appearing at 87 events and raising millions of dollars for candidates, according to his office, which did not have an exact figure immediately at hand. He has also raised about $3 million for the NRSC.
McConnell has also maxed out in some of the more competitive Senate races through his Bluegrass Committee, giving $260,000 to the NRSC, the RNC and Senate candidates, including Berg, Rehberg and Sen. Scott Brown (Mass.).
Other potential NRSC candidates include Sens. Jerry Moran (Kan.) and Marco Rubio (Fla.), Senate GOP sources have said.
Moran has contributed a total of $255,000 to Senate candidates and the NRSC over the past two years, according to his office. That includes $163,000 from his Free State PAC, as well as a $55,000 contribution to the NRSC from his campaign PAC, Moran for Kansas.
The Free State PAC has given to Virginia Senate candidate George Allen, New Mexico Senate candidate Heather Wilson and Rep. Jeff Flake, who is seeking the Senate seat in Arizona.
Rubio has raised $388,000 for Senate candidates. He gave $68,000 to candidates from his Reclaim America PAC and $320,000 to the NRSC over the past two years from the Rubio Victory Committee PAC, according to FEC filings. His office could not immediately confirm the figures.
Rubio has also helped raise other funds for candidates as well as campaigned with them. He was scheduled to host a fundraiser for Fischer today.
If Thune decides to run for a new post, one possible candidate for Conference chairman is Sen. John Barrasso (Wyo.), who is now Republican Policy Committee chairman.
Barrasso has given $431,000, including $231,000 directly to Senate candidates, $195,000 directly to the NRSC and a recent $5,000 contribution to GOP Senate candidate Tom Smith, who is running in Pennsylvania.
Barrasso has also been busy on the fundraising circuit, holding joint fundraisers around the country that raised significant amounts for GOP candidates and for the NRSC. In addition to traveling to Wyoming for his own campaign, Barrasso will be in Montana and North Dakota during the final stretch.
Sen. Roy Blunt (Mo.), the Republican Conference vice chairman, could also throw his hat into the ring for Conference chairman.
Blunt has given a total of $354,000 in federal contributions during 2012 election cycle. That number includes $184,000 to Senate candidates, $30,000 to the NRSC and $60,000 to the Target State Victory Fund, which is a joint effort to target specific races.
Another possible leadership candidate is Sen. Ron Johnson (Wis.), who in 2010 lost the vice chairman spot to Blunt by just three votes. Johnsonís Strategy PAC has contributed $28,000 to Senate Republican candidates, including Rehberg and Sen. Dean Heller in Nevada.