The Senate Leadership Fund is a Super PAC “spin-off of the GOP mega-group American Crossroads.” Its executive director, Steven Law, is a former chief of staff to Senate Majority Leader Mitch McConnell (R-KY) and also heads the two Crossroads groups and the One Nation dark money group.
As of early 2016, it seems unlikely that the SLF will succeed in monopolizing Republican Super PAC spending on Senate races. In September 2015, National Journal noted that “despite the creation of a single GOP conduit focused on the Senate landscape as a whole, former aides to vulnerable Republican senators have pushed ahead with plans to create individual super PACs focused narrowly on each incumbent’s reelection. Already, one-time advisers to three of the Democratic Party’s top targets in 2016—Pat Toomey of Pennsylvania, Rob Portman of Ohio, and Kelly Ayotte of New Hampshire—have formed super PACs dedicated to helping former bosses win second Senate terms. Supporters of two more incumbents, Mark Kirk of Illinois and Richard Burr of North Carolina, are readying their own super PACs, according to sources… Strategists with the individual super PACs maintain they have no plans to step aside, pointing to their own early fundraising as proof that they’re not going anywhere.”
As of January 31, 2016, the Senate Leadership Fund has $16.3 million cash on hand. The group’s biggest donors, at $2 million each, are energy companies Chevron and Petrodome Energy, as well as Warren Stephens. The group received millions of dollars from oil and gas companies at a time when the Republican Senate majority was seeking to lift the oil export ban.
 “New Rove-linked group spends $2M to boost GOP incumbents.” Alexandra Jaffe, CNN, 05/12/15
 “Fossil fuel company Super PAC gifts came before Congress ended the oil export ban.” Paul Blumenthal, The Huffington Post, 02/03/16