A leading GOP challenger to North Carolina Democratic Sen. Kay Hagan has dropped out of the race, despite a recent poll showing her tied with Hagan, who is up for re-election next year.A recent Public Policy Polling survey showed Hagan topping all potential Republican challengers for her seat except state Labor Commissioner Cherie Berry. Hagan and Berry tied at 45 percent each, according to the poll conducted May 17-19.But Berry announced last week that she won't run, according to The Charlotte Observer So far, only North Carolina House Speaker Thom Tillis and tea-party loyalist Greg Brannon have officially declared their candidacies.Meanwhile, U.S. Reps. Renee Ellmers and Virginia Foxx, state Senate leader Phil Berger, and Charlotte pastor Mark Harris are all said to be considering a run.Senate analyst Jennifer Duffy told The Charlotte Observer that Hagan -- who defeated Republican Sen. Elizabeth Dole in 2008 -- is vulnerable."I don’t think she’s been well defined because the 2008 race wasn’t about her. It was all about Dole," she said.The National Republican Senatorial Committee also believes Hagan is vulnerable. In fact, she is listed by the NRSC among seven Democratic senators they plan to heavily target."If it’s not the No. 1 race, it’s top three for sure," NRSC senior adviser Kevin McLaughlin told the Observer. "North Carolina is very, very ripe for the picking."