A week before the 2014 midterm elections, polls have Republicans with a better-than-even shot at expanding their lead in the US House of Representatives and winning control of the US Senate. But even with momentum, there are still roughly 10 races that are running in the low/mid single digits in the polls. Here are the best and worst case scenarios for Republicans in 2014.

Best Case Scenario

Republicans hold onto all of their seats that were up for re-election, including Kansas and Georgia which are much closer than anticipated.

Kansas wasn't on the map at the beginning of the year and Georgia appears headed to a runoff. After securing their own red seats, they will easily pick-up Montana, West Virginia, and South Dakota where incumbent Democrats opted not to run for re-election and all but handed half of the needed gains to the GOP. They turn red states Arkansas, Alaska, and Louisiana (after a likely runoff) to get to the 51-seat threshold.

Happy Warriors Cory Gardner in Colorado and Joni Ernst in Iowa pull off larger-than expected wins in swing states (5 points or more) while Scott Brown (NH) and Thom Tillis (NC) pull out last minute victories in late-night counting. Since this is the "best case scenario" we will throw in one final unlikely win. Though Michigan and Minnesota were once thought to be potentially competitive, it's actually New Mexico where the race has unexpectedly tightened to a 4-7 point race according to two polls. For the wave win, Allen Weh rides the coattails of the popular Governor, Susana Martinez, and her double-digit win pushes him over the top.

Democrats are caught sleeping having watched Martinez run away with the Governor race and assuming Udall was a shoe-in. Best case scenario: Republicans gain 11 seats en route to a 56-44 majority.

Worst Case Scenario

In the worst case scenario, Republicans suffer a repeat of 2012 where they also were expected to make large gains. Then, the GOP establishment had their way with the nominees but lost nearly every competitive race, including those in Virginia, Wisconsin, Florida, New Mexico, Michigan, North Dakota, Missouri, Montana, and Ohio. Without President Obama on the ballot - and perhaps thankfully so - the Democrats able to pull off the unexpected. The "Independent" in Kansas knocks off Pat Roberts and caucuses with the Democrats, while Michelle Nunn rides her name to a close victory in Georgia. Thought it appeared McConnell was pulling away, he wins by less than a point and the Democrats score a moral victory. The Democrats still lose West Virginia, Montana, and South Dakota, which were too far gone.

As for the other incumbents, New Hampshire and North Carolina wind up being easier to hold than originally thought, while Democrats also successfully defend all other races that were within 4 points, including Iowa, Alaska, and Colorado. They still lose Louisiana and Arkansas, but defy all expectations by holding onto the Senate by a 52-48 margin.

Likely Scenario

It would be a surprise to see either of the first two scenarios play out, but not shocking if it did. The Democrats landed the worst case scenario blow on Republicans in 2012. Of course, 2014 is different story. Democrats are running from Obama and refusing to say they even voted for the guy. The lack of a national election could depress turnout, especially among Democrats who remain far less enthusiastic about voting this year. So, what's likely to happen?

As in both scenarios, Republicans win the abandoned Democratic seats in West Virginia, Montana, and South Dakota. They also pick up Colorado and Iowa after impressive early voter operations propel the likeable candidates to victory over the semi-imploding opponents. Arkansas and Alaska are won by more than 5 points, while Louisiana goes into a runoff en route to a likely GOP win. This gives the GOP the 51 seats needed to win the US Senate. This leaves 4 seats - two by each party - that can really go either way. The 5 most recent polls in North Carolina have show two exact ties and three statistical ties, with Hagan ahead in two and Tillis ahead in one. In New Hampshire, a lack of early voting availability could benefit Scott Brown who has all of the momentum. He has closed to a tie in final week polls. Like Louisiana, Georgia looks headed for a runoff. The two candidates have traded small leads for weeks. Finally, anything can happen in Kansas. A 10-point victory for either Orman or Roberts would be no more surprising than a 1 point victory for either.

It would take a bit of luck for either party to win the four most competitive seats, but it wouldn't be a surprise if it happened, especially looking back at 2012. More likely is an even split of the four, but I won't predict what goes where. Further complicating matters is if Greg Orman wins in Kansas. He has vowed to caucus with the majority party. It's increasingly looking like that will be the Republicans. But the Democrats have given up a lot to support Orman. Still, it would probably serve in Orman's own best interest - should he win - to caucus with Republicans in the Republican-heavy state as promised. The likeliest scenario, once all the dust is settled, is a 53-47 majority for Republicans, with a range of +/- 2 seats for both parties.