It seems like a hundred polls are released every day now that the Iowa caucuses are less than a month away. Here's our guide to which ones matter and why.

Findings: Mitt Romney is still crushing his competitors in New Hampshire, with 38 percent of the vote to Newt Gingrich's 20 percent for second place. Jon Huntsman has 13 percent, and 11 percent are undecided. And Romney's moved ahead of Gingrich in Iowa.
Pollster: 7News/Suffolk; Rasmussen
Methodology: Interviews with 400 likely Republican voters in New Hampshire from December 10 to December 13; survey of 750 likely Republican caucus-goers in Iowa on December 13.
Why it matters: Romney's campaign might be able to relax a little bit. The New York Times reports that a mid-November poll showing Gingrich was competitive in New Hampshire -- a state Romney's team considered a lock -- "rattled" the campaign. Two days later, they announced the endorsement of the state's popular conservative Sen. Kelly Ayotte, something usually saved for just a couple days before voting. Huntsman, who has essentially a one-state campaign, is slowly gaining too. And while Romney still isn't campaigning much in Iowa, it's possible all the attack ads against Gingrich are working.
Caveat: Most polls of the state show Romney up by a much smaller number, an average of 10.8 points, Real Clear Politics shows. And Rasmussen leans right.

Findings: 40 percent of Republicans over 55 and conservatives pick Gingrich. Romney gets 21 percent and 23 percent of those guys respectively. 
Pollster: Gallup
Methodology: Phone interviews with 1,665 Republicans and Republican-leaning registered voters from December 5 through December 11.
Why it matters: Who would have thought of Romney as the youth candidate? The only age group he wins is Republicans aged 18 to 34, with 26 percent of their vote. But both Gingrich and Ron Paul get 20 percent of the kids. Gingrich is down slightly nationally, with 29 percent to Romney's 24 percent. But his strength lies with the people who actually vote -- old folks and "core identifiers with the Republican Party." 
Caveat: But it's only the Republican old folks who like Gingrich. On Wednesday, an NBC/Wall Street Journal poll found that while Romney beats Obama by 18 percentage points among seniors, Gingrich only beats him by 3 points.

Findings: Tim Kaine leads George Allen 47 percent to 42 percent in the race to replace Virginia Sen. Jim Webb.
Pollster: Public Policy Polling
Methodology: Automated telephone interviews of 400 Virginia voters from December 10 through December 12.
Why it matters: Early this year, Allen and Kaine were tied, but Kaine has slowly been gaining. Virginia is important for Obama -- he could lose Ohio and Florida and still be reelected if he wins this state and North Carolina. But a majority of Virginians disapprove of his job performance, and this fall, Democrats asked Obama not to show up in their districts when he went on a bus tour to promote his jobs plan.
Caveat: PPP is a Democratic-leaning polling company.