Castle, a former governor, is the states most popular Republican and the only candidate who could give Democrats a real run in the First State. A number of Republican Senators have already tried to convince Castle to make the jump to the other side of the Capitol, and the Congressman has said hes more likely to run for Senate or retire than he is to seek re-election. The NRSC is just hoping he doesnt pick retirement.
In California the NRSC also has a top potential recruit in former Hewlett Packard CEO Carly Fiorina (R). Shes well-known and could raise buckets of money for a race against Sen. Barbara Boxer (D), but she hasnt made a final decision yet on the race.
Colorado and Arkansas remain the two biggest question marks for the NRSC as September approaches.
Despite GOP dominance in the state when it comes to presidential elections, the Republican bench in Arkansas is weak at best. The list of Republicans who have filed for the race already certainly doesnt have Sen. Blanche Lincoln (D) supporters worried, and the Senators $3.2 million in the bank is a daunting figure to any Republican thinking of challenging her.
Now in her second term, Lincoln has taken some flak on the left for her wavering support of the Employee Free Choice Act but with the bill now on the back burner, Lincoln may not have to worry about the repercussions that a vote on the legislation could have on her electoral prospects this cycle.
When he was appointed in January to replace Sen. Ken Salazar (D-Colo.), Sen. Michael Bennet (D-Colo.) seemed like a juicy target for Republicans. Bennet, who previously served as superintendent of public schools in Denver, was not well-known outside the city, and it was unclear whether he could raise the money to compete in a statewide race. Eight months later Bennet seems to have put chatter about a possible primary behind him while Colorado Republicans have yet to rally behind a single candidate.
Aurora City Councilman Ryan Frazier (R) and Weld County District Attorney Ken Buck (R) are in the race, as is businessman Cleve Tidwell. Meanwhile former state Sen. Tom Wiens (R) has filed an exploratory committee. Outside that group, former Rep. Bob Beauprez, and radio host Dan Caplis are other GOP possibilities. Despite the many names currently being mentioned, none has yet to be championed by the national party and insiders admit that the field could continue to grow.
For their part, Senate Democrats who have a 60-seat majority in the chamber have fewer holes to fill when it comes to the recruitment game.
North Carolina remains the most glaring question mark for the party. Early polling has shown that Sen. Richard Burr (R) could be vulnerable in 2010 but a handful of House Members and statewide elected officials have all passed on the race.
The latest name being tossed around in Democratic circles is North Carolina Secretary of State Elaine Marshall (D), who is seriously considering taking on Burr.
Former Sen. Scott Brown, R-Mass., candidate for U.S. Senate in New Hampshire, holds his hand over his heart during the singing of the national anthem as he waits to take the stage for his town hall campaign rally with Sen. John McCain at the Pinkerton Academy in Derry, N.H., on Monday, Aug. 18, 2014.