With a majority of prognosticators (but not all of them) still predicting enough Republican gains to produce a change of control, it’s a good a time as any to look at some of the factors that could turn the trajectory around. I discussed several at TPMCafe yesterday:

What should prudent Republicans fear?
Money. You may find it shocking to learn that Democrats actually appear to have a national money and advertising advantage, at least in Senate races. But it’s true. Here’s how Charlie Cook of the Cook Political Report puts it in his National Journal column:

Perhaps the biggest untold story of this election is how so many Republican and conservative donors, at least those whose last name isn’t Koch, have kept their checkbooks relatively closed. In many cases, GOP candidates are not enjoying nearly the same financial largesse that existed in 2012, and in some races, they are well behind Democrats …
Many Republican and conservative donors appear to be somewhat demoralized after 2012. They feel that they were misled about the GOP’s chances in both the presidential and senatorial races that year, and/or their money was not well spent. In short, they are giving less if at all, and it has put Republican candidates in a bind in a number of places.

As for the Kochs, they haven’t outgunned Democrats as they expected either, as the Washington Post‘s Matea Gold explains:

Led by a quartet of longtime political strategists with close ties to Reid (D-Nev.), Senate Majority PAC has elbowed out other pro-Democratic groups and been on the leading edge of attacks against conservative donors Charles and David Koch. The group has become a fixed center of gravity in the left’s expanding constellation of super PACs and interest groups.
Perhaps most notably, the super PAC has held its own on the air against Americans for Prosperity, a conservative advocacy group that is the primary political organ of a network backed by the Koch brothers and other wealthy donors on the right. By the end of the summer, the two groups had run nearly the same volume of television ads nationwide, according to Kantar Media/CMAG data analyzed by the Wesleyan Media Project.
The “Republicans will get all the breaks down the home stretch” assumption a lot of folks are making could be based on mistaken ideas of GOP financial supremacy.

Turnout. We’ll soon know if the much-discussed $60 million Bannock Street Project of the DSCC, aimed at applying the targeted voter outreach efforts of the 2012 Obama campaign to the enormously critical task of reducing the party’s “midterm falloff problem,” is a myth or a miracle, or (more likely) something in-between. My own guess is that it’s likely to have the greatest impact in states with a previously under-mobilized minority vote (e.g., Arkansas and Georgia), or with an exceptionally strong pre-existing GOTV infrastructure (e.g., Iowa). Polling this year is generally showing a “likely voter” boost for Republicans that’s substantial but not as large as in 2010; reducing it even more — perhaps beneath the polling radar — is the Bannock Street Project’s goal.
Misinformation. It’s alway possible that the impression of a big year for Republicans is based on inadequate information, including spotty or inaccurate polls. That, of course, can cut both ways. FiveThirtyEight’s Nate Silver suggested this week that polling in Alaska over the last several cycles has consistently over-estimated Democratic performance. But on the other hand, an Atlanta Journal-Constitution survey giving Republican gubernatorial and Senate candidates in Georgia a small lead among likely voters estimated the African-American percentage of the electorate at 24 percent, significantly lower than in 2010, which seems, well, very unlikely. There’s also a very recent polling trend in Colorado, North Carolina, Iowa, and Michigan suggesting that these states may not look as good for Republicans as before, calling into question a general impression of a uniform pro-GOP drift.
Kansas. Nobody handicapping 2014 races as recently as three weeks ago factored in the possibility that Kansas, of all places, might become a sudden GOP sinkhole. Now Sen. Pat Roberts is in real and consistent trouble against independent candidate Greg Orman, as part of what appears to be a self-conscious revolt of moderate Republican voters who are also threatening to throw Gov. (and former Sen.) Sam Brownback out of office. Even if a national GOP intervention saves the Kansas ticket, this is money and effort that was supposed to be expended somewhere else.
And the sudden emergence of Kansas as a battleground raises on other possibility pre-triumphal Republicans should ponder:
Candidate Error. While Republicans avoided nominating a Christine O’Donnell or a Ken Buck this year (Senate nominees who were obviously weaker in a general election than their primary rivals), it’s not clear yet they didn’t unconsciously nominate another Todd Aiken or Richard Mourdock (purveyors of siliver-bullet-disaster gaffes) or Sharron Angle (someone with a rich record of extremist positions that negative ads could exploit). While Iowa Democrat Bruce Braley probably committed the most damaging single gaffe (his remark to Texas lawyers about an “Iowa farmer” chairing the Senate Judiciary Committee in the event of a GOP takeover) of the cycle so far, his opponent, Joni Ernst, seems capable of something just as bad, and also has Angle’s problem of telling wingnuts exactly what they wanted to hear for too long. And until Braley dissed Chuck Grassley, the most gaffe-prone Senate candidate in the country was probably Georgia’s David Perdue, who’s hardly out of the woods himself.

The tendency of Republicans to proclaim victory prematurely may turn modest gains into disappointment, if they aren’t careful.