North Carolina Secretary of State Elaine Marshall holds a small lead heading into the final week of her Democratic Senate primary with Cal Cunningham, but the two could be headed to a runoff.

A Public Policy Polling (D) survey and a SurveyUSA poll both show Marshall with a small lead in the primary, which will be held next Tuesday. But there remain plenty of undecided voters in the state, where neither candidate has had much in the way of a media presence.

Marshall leads Cunningham 23-19 in the SurveyUSA poll and 26-23 in the PPP poll. In both surveys, 34 percent of voters are undecided.

If enough of those voters go to other candidates, like attorney Kenneth Lewis, that could hold both Marshall and Cunningham below 40 percent, which would mean a two-candidate runoff on April 22. That's a long runoff, and it would all be time that the two won't be focusing their time and resources on Sen. Richard Burr (R-N.C.) and his $5 million war chest.

It's looking especially tough for Cunningham to win the primary outright next week. He would have to win at least half of those undecided voters and/or steal some support from his opponents.

Conversely, if it does go to a runoff, Cunningham will probably be the favorite. He has suffered from a lack of name recognition, but he has been raising money faster than Marshall. Presumably, he would be on TV more during the runoff, which would help him overcome Marshall's statewide profile.