Control of the Nevada Senate is up for grabs next week, with five races in play to determine whether Republicans can retake control of the upper chamber — or if Democrats can claim a big enough majority to exert political muscle over their GOP counterparts and Republican Gov. Brian Sandoval.Democrats hold an 11-10 edge. But the slim majority combined with redrawn districts and some tight voter registration numbers — not to mention thousands of nonpartisan voters — make the battle for control too close to call.In the Assembly, Democrats have a 26-16 majority, and Republicans are hoping to pick up …