Poll: GOP Senate candidates open up leads in key states

In Arkansas, Rep. Tom Cotton, R-Ark., leads incumbent Democratic Sen. Mark Pryor by five points among likely voters, 45 percent to 40 percent, with two minor candidates getting a combined 5 percent.

In Kentucky, Senate Minority Leader Mitch McConnell, R-Ky., is ahead of Democratic challenger Alison Lundergan Grimes by eight points among likely voters, 47 percent to 39 percent, with Libertarian David Patterson getting another 8 percent.

And in Colorado, incumbent Sen. Mark Udall, D-Colo., is up by six points over Rep. Cory Gardner, 48 percent to 42 percent.

To win control of the Senate, Republicans must pick up a net six seats, and they can do that by essentially running the table in states that President Barack Obama lost in 2012 – Alaska, Arkansas, Louisiana, Montana, North Carolina, South Dakota and West Virginia.