Washington ( CNN ) -- The battle for control of Congress is entering a final , frantic five-day stretch that favors Republicans but has room for plenty of surprises that could determine which party will run the Senate . The unsettled nature of so many individual contests at this late stage underscores the unpredictability of this election season . And Election Night could turn out to be a nail-biter that continues for days -- or even months . The themes that were expected to dominate this election cycle -- Obamacare and immigration -- are turning out to be duds . Meanwhile , threats posed by Ebola and ISIS -- hardly dinner table conversations a year ago -- are suddenly top issues . And on top of all that , add a mix of 2016 presidential drama as potential contenders barnstorm early voting states to help congressional candidates . The GOP is poised to extend its grip on the House and needs a net gain of six seats to take back the Senate for the first time since 2007 . Republicans are expected to easily take Democratic seats in Montana , South Dakota and West Virginia , leaving them needing just three more seats to build a Senate majority . But getting there could get tricky . North Carolina Democratic Sen. Kay Hagan is holding firm in a race many observers thought she would have lost by now , up four points in an Elon University survey over her challenger , Thom Tillis . In Georgia , Democrats believe that Michelle Nunn â€ ” one of the emerging stars of this election cycle â€ ” could beat Republican David Perdue . If neither candidate gets 50 percent of the vote a run-off election will take place in January . In Kansas , Senator Pat Roberts is still slugging it out against independent candidate Greg Orman and even the man most likely to become majority leader in a Republican Senate , Mitch McConnell , can not take re-election for granted in Kentucky . The loss of any of that trio would complicate Republican hopes in the Senate . Still , there are other pickup opportunities for Republicans . In Colorado , Democratic Sen. Mark Udall seemed to be in good shape just a few months ago . But now he 's down by seven points to Republican challenger Cory Gardner in a Thursday Quinnipiac University survey . The Denver Post had the race closer â€ ” with Gardner up two percent . In New Hampshire , Democratic Sen. Jeanne Shaheen is in a very tight race with former Massachusetts Sen. Scott Brown . Meanwhile , Arkansas Democratic Sen. Mark Pryor , fighting an uphill battle in an increasingly red state , was down between 13 and seven points to challenger Tom Cotton in two recent surveys . Other key states where Republicans have a good chance of picking up seats include Louisiana , Alaska and Iowa . Though the 2014 race is n't even wrapped up yet , the next election in 2016 is already unfolding as potential presidential candidates stump in key early voting states . New Jersey Gov . Chris Christie announced plans to blitz 19 states before Election Day , including Iowa , New Hampshire and South Carolina , which will play outsized roles in the presidential campaign . Jeb Bush , meanwhile , made waves by jabbing Hillary Clinton over her attitude towards business . On the Democratic side , Clinton , who increasingly appears to be waging an undeclared presidential campaign , tracked through Iowa this week -- the state that did most to doom her 2008 White House bid . Obama remained a sideshow , with his low approval rating making him unwanted by Democrats in swing states . So , he has been largely confined to raising millions of dollars for Democratic Party coffers , or stumping for candidates in liberal territory . On Thursday , Obama was headed to Portland , Maine , to campaign for Rep. Mike Michaud who is seeking to unseat Republican incumbent Paul LePage in a tight governor 's race . CNN 's Ashley Killough , Dan Merica and Jeremy Diamond contributed to this story .
The race for the Senate is unsettled going into the final week of November . Themes that were expected to dominate the campaign have n't resonated . Political climate still favors Republicans .