Ellis’s math looks like this. He believes 229 seats are either safe or likely in Democratic hands (you need 218 to form a majority in the House). On the Republican side, he counts 182 seats as safe or likely GOP. That leaves only 24 toss-up seats. Of those, Republicans currently hold 16 (8 incumbents and 8 open seats). Democrats control the other 8.
In addition to the 24, he writes that five GOP seats are already in the likely or safe Democratic category: NY-13 (Rep. Fossella, retiring), AK-AL (Rep. Don Young, incumbent), NY-25 (Rep. Walsh, retiring), VA-11 (Rep. Davis, retiring), AZ-1 (Rep. Renzi, retiring).
Ellis writes that McCain’s decline in the polls in the last month and the Democratic Congressional Campaign Committee’s money advantage could mean Democrats hold all of their 8 toss-ups and Republicans lose a good chunk of their 16. A net loss in the mid-twenties could push the Democrats’ advantage in the House to around 255-180, putting the GOP just slightly ahead of where it stood prior to the 1994 election. Before picking up a net 54 seats that year, Republican numbers in the House during the 1980s and 1990s ranged between a high of 192 following the 1980 election to a low of 167 after the 1990 midterm.
You'd think a Mark Foley-like scandal would stanch some of the bleeding. Not likely.