New poll numbers suggest that House Democrats are fighting back against the GOP “wave.”

Early last week, the Democratic Congressional Campaign Committee released internal polls, conducted by a number of firms, which showed Democrats ahead in races that early speculation had written off as all but lost to Republican challengers. According to these polls, Democrats had recovered the lead in Alabama’s 2nd District, North Carolina’s 8th District, New York’s 24th District, South Dakota’s At Large District, Illinois 10th District and Mississippi’s 1st District.

Only Rep. Tom Perriello of Virginia’s 5th District remains behind – by only 2 points. Perriello had been behind by double digits for most of the summer, and the last SurveyUSA poll from September 2nd, 2010 showed Perriello trailing his opponent, Robert Hurt, by an insurmountable 26-points.

Take internal polls with a grain of salt, and a 24-point swing from one poll to another challenges the credulity of both polls. Before you go and dismiss these results outright, there has been some confirmation of a counter-swing towards House Democrats.

In South Dakota, Rep. Stephanie Herseth Sandlin has been in trouble for months – she has been trailing in polls dating back to July. On August 6th, 2010, Rasmussen Reports released a poll of that race that showed Republican candidate Kristi Noem beating Herseth Sandlin by 9-points. Democratic pollster Anzalon Liszt’s September 7th poll of South Dakota showed Herseth Sandlin with an 11-point lead over Noem, completely inconsistent with all prior polls of this race. However, Rasmussen lent some credibility to that internal on Friday when it released a poll that showed Herseth Sandlin with a 2-point lead over Noem. All these numbers are within the margin of error, but show an unmistakable swing over to the Democrats.

On June17, Iowa’s 3rd District Republican candidate Brad Zaun’s camp released an internal poll that showed him 9-points over incumbent Democrat, Rep. Leonard Boswell. The Republican polling firm, American Future Fund released a poll on August 26, 2010, which showed Zaun with a double digit lead over Boswell. Last week, that same firm released another poll of the 3rd district that had Boswell beating Zaun by 9-points. The lack of disinterested polling in this race means all numbers are suspect. However, for AFF’s polls to vary that widely, and now to show Boswell ahead, could portend a comeback for Iowa Democrats. On September 9th, the AAF a survey of three out of Iowa’s five congressional districts, all held by incumbent Democrats thought to be in trouble this season. In all three, the Democrat came out ahead by healthy margins.

In Nevada, the Las Vegas Review Journal has been surveying the 3rd District since the early summer. On July 18, LVRJ released a poll that showed the incumbent freshman Democrat, Rep. Dina Titus, with a two point margin over her challenger, Joe Heck. On Monday, LVRJ and Mason-Dixon released a poll that showed Titus increasing her lead to 5-points, just on the edge of the poll’s 5-point margin of error. What’s more, Titus’s negatives fell from the last poll while Heck’s increased. Negative ads in that district may have had an impact on Heck’s negatives in this case, but the axiom that voter’s impressions of candidates are, for the most part, crystallized by Labor Day have proven incorrect in this race.

Polls, as is often repeated, are snapshots in time. They cannot reflect what will happen in November because there is a lot of ground to cover between now and then. If the Democratic Party retains the House in November, Herseth Sandlin, Boswell and Titus are three frontline members that will have to hold off their Republican opponents. If the polls are to be believed, that prospect is no longer impossible.

Noah Rothman is the online editor at C&E. Email him at nrothman@campaignsandelections.com