Two new independent polls of the Indiana Senate race show Richard Mourdock (R) losing significant ground to his opponent, Rep. Joe Donnelly (D-Ind.), in the wake of his statement claiming that pregnancies from rape are "something God intended to happen."
A Howey/DePauw University Battleground poll released Friday morning found Donnelly leading Mourdock 47 percent to 36 percent, up from a 2 point lead in September. Meanwhile, a new automated Rasmussen poll found Donnelly leading Mourdock by 3 points, up from a 5 point deficit just three weeks earlier.
Donnelly now leads Mourdock by 3.5 points in the HuffPost Pollster estimate, which is based on all available public polling, including internal polls from Mourdock's campaign that continue to show him with a narrow lead.
With all partisan polls filtered out of that estimate, Donnelly's lead expands to 5 points. HuffPost Pollster has officially shifted the rating of this race from "tossup" to "leaning Democratic."
If Donnelly goes on to win in Indiana, the Republicans' chances of winning a majority in the Senate are very low, as indicated by HuffPost Pollster Senate Outlook. Assuming that independent former Gov. Angus King of Maine -- who continues to lead in the polls -- caucuses with Democrats as expected, Republicans would need to win eight more competitive races to get to 50 seats, which would amount to a majority if Mitt Romney wins the presidency, with Paul Ryan casting the tie-breaking vote as vice president.
The Senate races in Nebraska, Nevada, Arizona, North Dakota, Wisconsin, Virginia, Montana and Massachusetts present them with their best opportunity to reach that number. However, Democratic candidates currently lead in five of those eight races, according to the most recent HuffPost Pollster estimates.
The GOP's more unlikely prospects lie in Senate races such as those in Connecticut, Ohio, Pennsylvania, Missouri and Florida, all of which feature Democratic candidates leading by at least 5 points.
However, if the Democrats manage to win all six races currently rated as "tossups" and all of the seats "leaning" their way, they could actually expand their majority by as many as four seats.
Here are the significant developments in other Senate races since Monday.
Elizabeth Warren (D) got a strong result from a new Suffolk University poll in Massachusetts, which shows her leading Sen. Scott Brown (R-Mass.) by 7 points, with only 1 percent of voters still undecided. Meanwhile, Republican-leaning Kimball Political Consulting found Brown ahead by 2 points. The two candidates agreed to cancel their final debate, scheduled for Oct. 30, due to damage caused by Hurricane Sandy, and Brown refused to reschedule the debate for Thursday. With no other major public events scheduled between now and Election Day, the focus turns to the two campaigns' highly touted turnout operations, especially in the aftermath of the storm. Warren currently leads Brown by 4.2 points in the HuffPost Pollster estimate and this race is still rated as "leaning Democratic."
Former Gov. Tommy Thompson (R) has pulled nearly even with Rep. Tammy Baldwin (D-Wis.) in the open Wisconsin Senate race, according to recent polls. Baldwin's lead has shrunk to just 1 point in the current HuffPost Pollster estimate, and this race rating has shifted from "leaning Democratic" to "tossup." Of the five polls taken of both the state's presidential and Senate races over the last week, Thompson has outperformed Mitt Romney by an average of exactly 5 points. If Romney even comes within a few points of winning Wisconsin, it significantly boosts Thompson's chances. If Romney wins the state, it's hard to see how Thompson loses.
Polls also show the open Virginia Senate race as having tightened over the past few weeks. Former Gov. Tim Kaine (D) now leads former Sen. George Allen (R-Va.) by 1.4 points in the HuffPost Pollster estimate, but his fate now appears to be tied to President Barack Obama's performance, who currently leads Romney by a similarly slim margin in the state.
The Senate race in Montana continues to be one of the closest races in the country. Since September, neither Sen. Jon Tester (D) nor Rep. Denny Rehberg (R) has led by more than a 3 point margin in any publicly released poll. This past week, two independent polls, from Pharos Research Group and Rasmussen, both found Tester leading Rehberg by just 1 point. Tester holds a statistically insignificant 1.9 point lead in the current HuffPost Pollster estimate of the race.
While former Sen. Bob Kerrey (D) saw some encouraging polling numbers last week in Nebraska, a new automated We Ask America poll found him trailing state Sen. Deb Fischer (R) by 13 points -- similar to the margins she enjoyed over the summer. Since this race has been so sparsely polled, this result was enough to shift Fischer's advantage up to 10 points in the HuffPost Pollster estimate and keep this race rated as "strong Republican."
HuffPost Pollster rates a race as a "tossup" if the polling margin separating two candidates is less than 3 percentage points in the Pollster estimate and there have been at least five polls in that state in the last three weeks. A race is designated as "leaning" toward one party if a candidate is leading by 3 to 6 percentage points in that estimate. If a candidate is leading by more than 6 percentage points, it is rated as "strong" Democrat or Republican.
If there have been fewer than five polls in the last three weeks in any given race, composite ratings are used from three respected election handicappers: the Cook Political Report, the Rothenberg Political Report and Larry Sabato's Crystal Ball.
For more details and polls of all 33 Senate races, visit the HuffPost Pollster's Senate Outlook page.