Jim Gergahty, who will speak to the John Locke Foundation’s Shaftesbury Society later this month, probes for National Review Online the latest numbers on Republicans’ prospects for retaking control of the U.S. Senate.

Republicans begin with 41 seats safe or not up for reelection, and we’re likely to be able to throw Kansas’s Pat Roberts and Mississippi’s Thad Cochran onto that list — presuming Cochran can overcome bad blood from his runoff-primary win and Roberts survives his primary challenge. That puts them at 43 seats.

Begin with the three seats currently occupied by Democrats where the GOP is favored heavily: West Virginia, South Dakota, and Montana. In West Virginia, the last survey came in mid-May, when the West Virginia Poll found Republican Shelley Moore Capito ahead by 11 percentage points over Democrat Natalie Tennant. In South Dakota, the lone poll released in June showed Republican former governor Mike Rounds ahead by 15 over Democrat Rick Weiland. Finally, in Montana, John Walsh was appointed to fill out the final months of Max Baucus’s term. In the lone poll released since April, Rasmussen found Republican representative Steve Daines leading Walsh by 18.

This puts them at 46 seats. Now move to the three Democratic incumbent senators widely perceived to be among the most vulnerable this cycle — all trailing, but modestly.

In Louisiana, Mary Landrieu is expected to face an early-December runoff with GOP representative Bill Cassidy. (Under Lousiana’s election laws, there are no primaries, and if no one gets 50 percent on Election Day, the top two finishers go to a runoff.) Only two polls have surveyed the state’s voters on this race since early June: GOP firm Magellan Strategies put Cassidy up by 6; Democratic firm Public Policy Polling had the candidates tied.

In Arkansas, incumbent Democrat Mark Pryor faces Representative Tom Cotton, and after a slew of polls in the spring, only one has been conducted since June. Magellan Strategies puts Cotton up 4.

In North Carolina, incumbent Kay Hagan, a Democrat, faces GOP challenger Thom Tillis, and here there’s been a relative plethora of polls, all offering modestly good news for Hagan. Magellan Strategies puts her up 1, PPP puts her up 4, and Civitas, a Republican firm, puts her up 4 as well. …

… Sweeping those three races would put Republicans at 49 seats, and needing two more to control the U.S. Senate beginning in January 2015. (Vice President Joe Biden would break ties in a chamber split 50–50.)

While the Republicans have many opportunities to win those next two seats, GOP challengers in those races have steeper climbs.