Polls are snapshots, but they also tell a story. And if the results of eight polls can be considered a microcosm of the 60 to 75 competitive House races this fall, then Democrats — two months out from Election Day, anyway — seem to be in a good position to make gains.

Working with SurveyUSA, an automated polling firm, Roll Call during the past two weeks ran polls on eight hotly contested Congressional races. The polls found that Democrats are narrowly — but clearly — ahead in two GOP-held districts, New Mexico’s 1st, a marginal open seat, and Colorado’s 4th, where the incumbent, Rep. Marilyn Musgrave (R), seems to be in terrible jeopardy. Democrats also led in Florida’s 21st district, held by Rep. Lincoln Diaz-Balart (R), though the lead was within the poll’s 4-point margin of error.

Two freshman Democratic Members who seized traditionally Republican districts in 2006 — Reps. Christopher Carney (Pa.) and Nancy Boyda (Kan.) — were also ahead, though not by comfortable margins, meaning that the GOP has a legitimate chance of winning those seats back.

The polls also offered some good news to House Republicans. In two open-seat races in GOP-held districts that the Democrats have talked boldly about competing — Alabama’s 2nd and Missouri’s 9th — the Republican nominees held substantial leads. And the Republican was also leading in the race to replace retiring Rep. Jim Ramstad (R-Minn.), though his lead was within the margin of error, and that race — in which a serious third-party candidate is competing — is likely to be a tossup all the way to Election Day.

Polls can be controversial, and some of Roll Call’s were no exception. Three of the eight polls brought swift reactions from campaigns and political operatives who disagreed with the results.

After Roll Call published its poll showing Carney with a 4-point lead over businessman Chris Hackett (R), Carney’s campaign released a recent poll showing the incumbent with a 2-1 advantage.

When Roll Call showed Diaz-Balart trailing former Hialeah Mayor Raul Martinez (D) by 2 points despite the Republican lean of his Miami-area district, the Congressman’s campaign blasted the SurveyUSA poll for interviewing too many Democrats. It also released its own poll from June that showed Diaz-Balart with a healthy lead.

But the most notable outcry came from several Democratic strategists who blasted Roll Call’s poll on Alabama’s 2nd district, which showed state Rep. Jay Love (R) with a 17-point lead over Montgomery Mayor Bobby Bright (D) in the race to replace retiring Rep. Terry Everett (R). Their chief complaint: The poll’s sample size of African-American voters — found in the Roll Call poll to be 16 percent of the electorate — was too small in a district where blacks represent more than 29 percent of the population, particularly in a year when the presidential candidacy of Sen. Barack Obama (D-Ill.) is expected to produce a larger-than-usual black turnout.

Democratic polls on the race that have not been made public show a much closer contest, and those polls assume a model using higher African-American turnout.

Asked to recrunch its polling numbers, SurveyUSA calculated that if African-American voters constitute 24 percent of the district’s electorate, Love’s margin over Bright would be 50 percent to 44 percent. If blacks represented 27 percent of the electorate, Love would lead 49 percent to 46 percent. And if blacks were 30 percent of the electorate, the contest would be tied, 47 percent to 47 percent.

In much the same way that it’s possible to get a grand jury to indict a ham sandwich, as the old legal saying goes, it appears it’s also possible to get a poll to say just about anything.

But while partisans may have quarreled with some of the results in the Roll Call polls, some of the conclusions in the surveys were universal and inescapable.

For starters, the job-approval rating for Congress was shockingly low, ranging from 12 percent to 20 percent. President Bush’s ratings were in the 30s in most of the polls.

The polls also found that voters are concerned about the economy above all other issues; nothing else was even close. They also found that, despite the Republicans’ rhetoric about the necessity of drilling for more oil, most voters prefer a Congressional candidate who advocates a variety of alternative sources of energy.

Roll Call plans to poll several more Congressional races between now and Election Day.