Washington (CNN) -- Democratic Sen. Kay Hagan is clinging to a narrow lead over Republican challenger Thom Tillis in North Carolina, a new CNN/ORC International poll shows.
Hagan led with 48% support to 46% for Tillis, the state House speaker, in the survey of 559 likely voters, conducted Oct. 27-30 and with a margin of error of plus or minus four percentage points. Libertarian Sean Haugh polled at 4%.
Hampering Tillis is an underwater favorability rating. Just 43% of those surveyed said they have a favorable view of him, compared to 50% who view him unfavorably. That's a dramatic shift since a September CNN/ORC International poll that put his favorability rating at 47%, with just a 40% viewing him unfavorably.
"Hagan seems to have done a good job of defining her lesser-known challenger in an unflattering light," said CNN Polling Director Keating Holland.
"The jump in Tillis' unfavorables is highest among women (a 12-point increase), lower-income voters (12 points), and particularly in the suburbs (16 points)," Holland said.
Hagan, meanwhile, is viewed favorably by 49%, while 48% say they view her unfavorably. She could be dragged down, though, by President Barack Obama's unpopularity. Just 42% said they approve of Obama's job performance.
Tillis leads among suburban and rural voters, earning 49% support in each category compared to 43% support for Hagan among suburban voters and 44% with rural voters. Hagan, though, holds a massive lead in urban areas, where she has 59% support to Tillis' 37%.
Hagan leads by 16 percentage points among women and Tillis is up 12 points with men.
North Carolina is one of several states that President Barack Obama won at least once -- Colorado, Iowa and New Hampshire are the others -- where Republicans are hoping to grab Senate seats previously held by Democrats.
Their success in those states could determine whether the GOP captures the six seats it needs to become the Senate's majority party for Obama's last two years in office.
The CNN/ORC International results come after several other polls have put Hagan ahead. An Elon University survey conducted Oct. 21-25 put the freshman senator up 45% to 41%, while a Rasmussen Reports poll showed her up 47% to 46%.
The race has been the most expensive of the 2014 midterm cycle, with spending by the campaigns, national committees and outside groups topping $100 million.