The Republican Party knows it must gain six seats in the Senate to gain a majority, but as things stand, they are in danger from Tea Party right wingers, who might defeat them in primaries this year, and then could lose safe seats to the Democrats!
This includes Senate Republican leader Mitch McConnell of Kentucky; Senator Thad Cochran of Mississippi; Senator Lindsey Graham of South Carolina; Senator Lamar Alexander of Tennessee; Senator John Cornyn of Texas; as well as open Republican Senate seats (due to retirements) in Georgia and Nebraska.
The wackiest candidates against these Senators are Matt Bevin in Kentucky; Lee Bright in South Carolina; and Steve Stockman in Texas. But also, three Georgia Senate competitors in Georgia are all wacky—Paul Broun, Phil Gingrey, and Jack Kingston, all sitting Georgia House members, with the only good thing is that two will be eliminated from Congress by running in the Senate primary.
So in theory, instead of gaining six seats, the GOP could lose up to seven seats if the Tea Party succeeds in defeating solid conservative Republican Senators, or in the case of Nebraska and Georgia, solid conservatives who are retiring.