Kansas independent Greg Orman continues to hold an edge in his quest to unseat Sen. Pat Roberts (R-Kansas), according to most recent surveys on the race.

An NBC/Marist poll released Sunday finds Orman leading Roberts by 10 points, 48 percent to 38 percent, among likely voters. Five percent chose libertarian Randall Batson, and the remaining voters were undecided or opting for yet another candidate.

Orman's lead speaks to the depth of the image problem faced by Roberts, who this year fended off an acrimonious tea party challenge, as well as criticism following the revelation that he didn't own a home in Kansas.

According to the NBC/Marist poll, likely voters view Roberts unfavorably by a 10-point margin. In contrast, they view Orman favorably by a 20-point margin -- although one-quarter still don't have an opinion of him. More than half of those who support Orman said they do so mainly because they dislike Roberts.

The survey also shows a more general sense of disaffection toward the GOP. While Democrats are about as unpopular as you might expect in Kansas -- 54 percent of registered voters disapprove of Barack Obama's record as president -- voters are also 6 points more likely to disapprove of Republicans in Congress than of Democrats in Congress.

Most polling has found Orman ahead by several points since the Kansas Supreme Court ruled that Democrat Chad Taylor, who withdrew from the race, could remove his name from the ballot, but NBC/Marist results give him his largest advantage to date.

A second poll released Sunday, however, finds Roberts and Orman tied. The New York Times' Nate Cohn notes one possible reason for the disparity: The second survey, conducted by YouGov for CBS and the Times, finds 19 percent of Democrats undecided, much higher than in other polls.

HuffPost Pollster's Senate model, which incorporates all publicly available polling, gives Orman a lead of just under 4 points over Roberts.

Orman has said he'll caucus with the majority party in the Senate if elected, but remains mum on which side he'll choose if he ends up as the deciding vote, saying only that he'll work with "whichever party is willing to actually go to Washington and start trying to solve problems." The question is more than a hypothetical: The Pollster model gives him a 12 percent chance of determining whether Republicans retake the Senate.