Democrats in key Senate races are showing some strength in the final stretch of election season -- but it may not be enough to keep the chamber . A new CNN/ORC poll released Friday shows Democrat Michelle Nunn leading Republican David Perdue 47 % to 44 % among likely voters . A WAFB poll out this week in Louisiana found incumbent Democrat Mary Landrieu four points ahead of Republican Bill Cassidy . And a recent Courier-Journal/Survey USA poll in Kentucky found Democrat Alison Lundergan Grimes trailing Senate Republican leader Mitch McConnell by just one point . It 's enough to make Democrats feel cautiously optimistic about their ability to hold onto the Senate . But there 's a problem : in two of the races -- Georgia and Louisiana -- Democrats will need to win at least 50 % of the vote to avoid a runoff . And neither candidate is clearing that threshold in polls . The stakes are huge . Democrats could upend Republican hopes of picking up the net gain of six seats needed to claim the Senate if they find a way to succeed in these races without a runoff . The good news-bad news scenario is reflected in today 's Georgia poll . `` It is a surprising show of strength for a Democrat in a state in which no Democrat has won a statewide election in over a decade , '' said CNN Polling Director Keating Holland . Democratic and Republican consultants credit Nunn , daughter of former senator Sam Nunn , with running a strong campaign . She gained momentum in recent weeks by slamming one of former CEO Perdue 's supposed strengths : his business record , and accused him of shipping US jobs overseas . The CNN poll also shows Nunn beating Perdue 51 % to 47 % in a run-off election that will take place on Jan. 6 if neither candidate wins in the first round . The data , however , is based on those likely to vote in November and the electorate in run-off elections typically differs from first round votes . As Nunn inches closer to the 50 % threshold , her fate could lie with libertarian candidate Amanda Swafford , who is polling at 5 % of likely voters . No one knows whether Swafford 's supporters will gravitate to Perdue or simply stay home -- and their decision could have big implications for who wins the race . An idiosyncratic election system is also a problem for Democrats in Louisiana , where Sen. Mary Landrieu led the last five polls ahead of the state 's open primary , which will send two candidates to a run-off if no one wins 50 % of the vote . An outright win is eluding Landrieu . Though she 's ahead of Cassidy , recent polls show her garnering only support in the high 30 % to low 40 % range . Even worse for Landrieu , when voters are asked if they plan to vote for Landrieu in the run-off , she trails Cassidy by between three and nine percent . Robert Hogan , a political science professor at Louisiana State University , said Landrieu has seen her state rapidly trend more Republican since she won the seat for the first time in 1996 , and says a run-off may be one step too far for her . `` I think that her support is probably around 42 or 43 percent , '' Hogan said . The runoffs will be even more crucial if the results determine control of the Senate . Such a scenario would unleash a torrent of national attention , campaign cash and duels by top party surrogates , which could produce cliffhanger election nights weeks after voters go to the polls in November .
Candidates in Louisiana and Georgia must win 50 % to win a runoff . Democrats in those states are ahead in some polls but have n't cleared 50 % .