In the latest swing state polls, Obama is up by 8 in Virginia and five in Michigan, and Romey leads by 2 in Colorado and 1 in Florida. While in the Massachusetts Senate, Elizabeth Warren keeps her lead. Here's our guide to today's polls and why they matter. 

Findings: Obama leads in Virginia by eight points — 52 percent to 44 percent — among likely voters. 
Pollster: Washington Post with sampling, data collection, and tabulation by Abt-SRBI. 
Methodology: Telephone poll of 1,104 adults including 847 likely voters, from September 12 to 16, with a margin of error of +/-4 percent. 
Why it matters: Virginia is what Nate Silver in a New York Times Magazine story labels a "New Breed" swing state: "In these states, which Obama carried in 2008 but Kerry and Gore lost, swift demographic changes have become manifest." Laura Vozzella and Jon Cohen of the Post explain that as far as their poll goes: "Obama’s steady lead suggests that an unprecedented barrage of TV ads and dozens of in-person visits have yet to change the bottom line in the key battleground state." 
Caveat: Vozzella and Cohen do caution that "The parity on the economy underlines a lingering vulnerability for Obama, particularly as looming defense cuts threaten the industry and the state’s economy as a whole." Silver notes that Virginia "has also been a headache for pollsters" this year because of erratic results, and in the Real Clear Politics average Obama leads by 2.8 points. 


Findings: Romney is up in Colorado 47 percent to 45 percent.
Pollster: Rasmussen 
Methodology: Automated poll of 500 likely Colorado voters on September 17 with a margin of error of +/-4.5 percent.
Why it matters: Silver puts Colorado in the same category as Virginia explaining, "If demographic changes favor the president in Colorado, the state’s anti-incumbent spirit — it voted for Bill Clinton as the challenger in 1992 but not as the incumbent in 1996 — does not." Rasmussen points out that previous polls from the state have showed a tie between the two candidates, with Romney now very slightly ahead. 
Caveat: Rasmussen leans Republican. 


Findings: Obama leads Romney by 47.5 percent to 42.3 percent in Michigan.
Pollster: Marketing Resource Group 
Methodology: Poll of 600 likely voters September 10 with a margin of error of +/-4 percent.
Why it matters: A GOP candidate hasn't won Michigan since George H.W. Bush in 1992, David Eggert of MLive.com notes, and Tom Kludt at Talking Points Memo points out "Obama has long been the favorite in Michigan — despite Romney's personal connection to the state — due in large part to his administration's successful restructuring of the U.S. automakers." In his analysis, Silver writes: "In Michigan, Romney’s opposition to the auto bailout may be too much of an albatross." 
Caveat: Michigan probably won't be crucial this year. Silver gives Michigan only a 1 percent chance of "determining the Electoral College winner."


Findings: A Gravis Marketing poll out of Florida shows Romney with 47.7 percent and Obama with 47.1 percent in the state. 
Pollster: Gravis Marketing 
Methodology: Automated telephone poll of 1,728 likely voters, September 15 to 16, with a margin of error of about +/-2.5 percent.
Why it matters: Florida, according to Silver has a 20 percent chance of determining who wins the Electoral College, and this poll indicates a dead heat. 
Caveat: Recent polls in the state have mostly put the race in neck-and-neck status, but the RCP average has Obama in the lead by 1.4 points, opposed to this poll's very slight Romney lead. 


Findings:  Another poll shows Elizabeth Warren leading Scott Brown in the Massachusetts Senate race, up 48 percent to his 44 percent. 
Pollster: Suffolk University/7NEWS
Methodology: Telephone poll of 600 likely voters September 13 through 16 with a +/-4 percent margin of error. 
Why it matters: This poll up from the news yesterday that Warren had taken a post-convention lead. Sean Sullivan at the Washington Post writes, "The Suffolk poll was conducted Thursday through Sunday, just as Warren launched the first of two new ads that represented a change of pace from previous commercials. The new spots relied more on supporters making the case for Warren, whereas in most of Warren’s summer ads, she was the main messenger." Sullivan later sets out to explain the move toward Warren as such: "Voters identifying as Democrats appear to be moving more heavily toward Warren. Voters who plan to support Obama (many of whom are also Democrats) are coalescing behind Warren as well. In other words, Brown’s much-need crossover support appears to be weakening." 
Caveat: Warren's lead is still within the poll's margin of error.