As we inch toward November, it looks as if a couple of dozen House races will determine whether Democrats will have a terrific night or merely a good one. Expectations continue to change, and the bar is getting very, very high for Democrats.

[IMGCAP(1)]Eighteen months ago, the idea that the Democratic Congressional Campaign Committee might net eight or 10 House seats, after the 30 seats the party picked up in 2006, was seen by most Democrats as a reason for popping corks and opening a case of champagne.

But now, gains of that magnitude would be a distinct disappointment for rank-and-file Democrats, and it would be GOP strategists who would heave a huge sigh of relief at losses limited to those levels.

Some pickups already seem like slam-dunks for Democrats. But here are a dozen races to watch to see whether Democrats are having a big night in the House races:

Florida’s 25th district: Rep. Mario Diaz-Balart (R) Vs. Joe Garcia (D). With three Cuban-American seats in play in South Florida, Mario Diaz-Balart’s isn’t the hardest (that would be brother Lincoln Diaz-Balart’s) or the easiest (that would be Ileana Ros-Lehtinen’s) for the GOP to hold. A victory by Garcia would be a good sign for Democrats.

New York’s 26th: Rep. Tom Reynolds (R) is retiring. Republicans increasingly believe that they can hold this Western New York open seat. Their candidate, businessman Chris Lee, is running on three ballot lines — Republican, Conservative and Independence — and the district certainly tilts to the GOP. Democrat Alice Kryzan won her party’s nomination because two better-funded candidates destroyed each other.

Illinois’ 10th: Rep. Mark Kirk (R) Vs. Dan Seals (D). Kirk would win this rematch against Seals nine out of 10 times, but this could be the year that he doesn’t. The district is competitive, and Kirk will have to run far ahead of the rest of the GOP ticket. A Kirk loss would be bad news for another vulnerable GOP incumbent, Rep. Dave Reichert (Wash.).

New Jersey’s 7th: Rep. Mike Ferguson (R) is retiring. Democrat Linda Stender narrowly lost to Ferguson last time and faces a different foe this year: state Sen. Leonard Lance, a well-regarded moderate. But Lance had a tough primary and therefore began his general election far behind in cash. Still, polling shows this race very close, and the general Republican bent of the district means that Lance may be able to swim against a strong anti-GOP current.

New Hampshire’s 1st: Rep. Carol Shea-Porter (D) Vs. Jeb Bradley (R). Shea-Porter came in on the Democratic wave in 2006, and she faces the man she beat two years ago. Polling suggests a close race, and if Bradley can come back and oust her, it could be a sign that the Democratic wave of 2008 peaked far too early.

Maryland’s 1st: Rep. Wayne Gilchrest was defeated in the GOP primary. This very Republican open seat could fall to Democrats, in part because Republicans are divided. Gilchrest lost his primary to conservative state Sen. Andy Harris. The Congressman has endorsed Democrat Frank Kratovil, and the Democratic Congressional Campaign Committee is invested in this race, in part because DCCC Chairman Chris Van Hollen and House Majority Leader Steny Hoyer are both from Maryland.

Ohio’s 1st: Rep. Steve Chabot (R) Vs. Steve Driehaus (D). Working-class voters and the size of the African-American vote could be keys to this district. Chabot won re-election with more than 52 percent last time in a bad political environment, and his defeat next month would signal an even bigger Democratic wave. Driehaus is a state legislator who insists he can take votes from Chabot’s base.

Ohio’s 2nd: Rep. Jean Schmidt (R) Vs. Victoria Wulsin (D). Schmidt narrowly beat Wulsin last time (by a single point) in a district President Bush carried with 64 percent in 2004. Both nominees have flaws, but if Wulsin wins, it’s a sign of either very low GOP turnout or more Republicans turning against their party. Either way, that would be disastrous news for Republicans.

New Mexico’s 2nd: Rep. Steve Pearce (R) is running for Senate. Polling suggests that Democrat Harry Teague has a narrow lead in this Republican-leaning district, and he is offering a moderate-to-conservative message. Republican Ed Tinsley hopes to make this a liberal vs. conservative choice, but that isn’t easy in an environment when people are worried about their jobs, mortgages and retirement accounts.

Kentucky’s 2nd: Rep. Ron Lewis (R) is retiring. Two state Senators, Republican Brett Guthrie and Democrat David Boswell, are locked in a tight contest. In any normal year, Guthrie probably would win, but national Democrats have dumped a lot of cash into this race to try to pull Boswell across the finish line, and they certainly have a chance of doing so. A Republican loss here would be a horrible sign for GOP prospects in New Mexico’s 2nd district.

Nebraska’s 2nd: Rep. Lee Terry (R) Vs. Jim Esch (D). Terry defeated businessman and veteran Esch by more than 9 points last time, but the worsening national mood has Democrats thinking upset. Polling shows that Terry isn’t safe, and some Republicans complain that he doesn’t run hard enough. But if Terry loses here, Democrats certainly should win 30 seats.

West Virginia’s 2nd: Rep. Shelley Moore Capito (R) Vs. Anne Barth (D). Thinking 30 seats-plus for Democrats? Capito’s district is a good place to look. Polling has shown that the Republican incumbent looks like winner, so if she is upset, you know something huge is happening.

Stuart Rothenberg is editor of the Rothenberg Political Report.