Colorado, Iowa, North Carolina and New Hampshire are perhaps the closest races in the country right now.
That's why national Democrats are flooding these states with cash from Hollywood, Tom Steyer, and other liberal special interests. The DSCC has spent well over half of their TV expenditures in these four states — i.e., approximately $25 million in false and negative ads about Joni Ernst, Cory Gardner, Scott Brown and Thom Tillis.
Despite this onslaught of Democratic spending, these races remain a dead heat. That's a really bad sign for Mark Udall, Bruce Braley, Jeanne Shaheen and Kay Hagan. Democratic incumbents are spending millions to tread water. Treading water faster doesn't build momentum.
Incumbent senators are a known quantity to voters, but challengers are introducing themselves to the electorate. Voters who are familiar with an incumbent but do not support them on the ballot are searching for a new senator. This group of voters traditionally breaks against the incumbent by a 2-1 margin.
History tells us that for every four undecided voters, one will typically vote for the incumbent, two will vote for challenger, and one will not vote.
This history means that for every point the incumbent is short of the 50 percent threshold, they need 4 percent in the undecided category to make it up. If an incumbent is at 48 percent, they need the undecided number to be at 8 percent; an incumbent at 47 percent needs 12 percent, etc.
There's even more bad news for Democratic incumbents, though. The political environment is bad for them. Some of them (like Kay Hagan and Mark Udall) have high unfavorables. At this very moment, undecided voters are just beginning to tune in, and between 60-70 percent are likely to end up voting for the challenger.
What's the bottom line? Undecided voters will decide the size of the GOP wave.
That's why it is important to look at polls in their proper context. Dan McLaughlin provided an in-depth analysis of this reality
, tracking results back to the 2002 cycle:
A review of the mid-September polls over the last six Senate election cycles, all of which ended in at least a mild "wave" for one party, shows that it is common for the "wave party" to win a few races in which it trailed in mid-September – sometimes more than a few races, and sometimes races in which there appeared to be substantial leads, and most frequently against the other party’s incumbents. Whereas it is very uncommon for the wave party to lose a polling lead, even a slim one, after mid-September – it has happened only three times, one of those was a tied race rather than a lead, and another involved the non-wave party replacing its candidate on the ballot with a better candidate. If these historical patterns hold in 2014, we would therefore expect Republicans to win all the races in which they currently lead plus two to four races in which they are currently behind, netting a gain of 8 to 10 Senate seats.His final conclusion is great news for the GOP
If 2014 follows the path of 2002, 2004, 2006, 2008, 2010, and 2012, we would expect to see between 53 and 55 Republicans in the Senate in 2015.