‘Hey Jim, could you put together a list of House races where it’s either an open seat race or a vulnerable incumbent?” the editors ask, oh-so-innocently.

Do they have any idea how much work that entails? Scott Brown won a Senate race in Massachusetts by a healthy margin this year — you can find a list of winnable House seats by starting at page one of Michael Barone’s Almanac of American Politics and working your way to the index. It might be shorter to list the Democrats who aren’t vulnerable this year.

Once you add up the upcoming special elections, the open-seat races, and the races where there’s some indicator of trouble for a Democratic opponent — a particularly strong challenger, favorable district demographics, surprising fundraising numbers, a particularly weak Democratic incumbent, or a combination of these factors — you come up with more than 90 House races. If the GOP wins only half the seats listed below, they win back the House.

SPECIAL ELECTIONS
Two early measures of the public mood arrive this month. The first is John Murtha’s open seat in Pennsylvania’s 12th district, which the National Republican Congressional Committee (NRCC) characterizes as “more of a national referendum on Pelosi and Obama.” Polling puts Republican Tim Burns narrowly ahead of Democrat Mark Critz, but in a district full of white, working-class conservative Democrats, it is likely to be a close finish. Critz is in a strange position, having to run ads touting that he opposed the health-care bill, but also declaring at a recent candidate forum that he would not vote to repeal the health-care bill. He has also apologized for an ad that mischaracterized Burns’s past statements on taxes.

Then there’s the special election for Neil Abercrombie’s open seat in Hawaii’s first district, where Charles Djou is trying to win a plurality in an odd, all-vote-by-mail special election against two well-known Democrats. The NRCC calls Djou “an exceptional candidate doing an exceptionally good job”; they think that the electorate currently splits, with roughly a third for each candidate but Djou ahead by a few points, and that’s a more modest assessment than that of a poll out May 2, which put Djou ahead by 8. The pollsters credit Djou for a “good ground game.”

OPEN SEATS
Paul Hodes’s open seat, New Hampshire: Democrats will have a tough three-way primary, while Charlie Bass, who represented this district for twelve years, appears to have the inside track on the GOP side. A University of New Hampshire poll puts Bass up 17, and the Granite State is souring on Obama and Democrats in general quickly.

Bill Delahunt’s open seat, Massachusetts: There aren’t that many experienced Republican politicians in Massachusetts, but three of them came out of the woodwork to run against Delahunt after Scott Brown’s win. Two state legislators and guy with the last name “Kennedy” — no relation to the famous family — will compete on the Democratic side. Brown won almost 60 percent of the vote in this district.