

Rep. Barbara Comstock (R-Va.) is one of the Republicans to watch when gauging whether this could be a year of big losses for the House GOP. (Cliff Owen/AP)

Following changes in the “generic ballot” poll question is one way to track the fight for the House, but an alternate way is to look at key races at various levels of competitiveness that should indicate whether a wave is developing and, if it is, how big it might be.

Here is a scorecard of a few tiers of GOP-held House seats to watch over the next 2 1/2 months. They run from near certain Democratic takeovers to Democratic long-shot opportunities.

Should be a slam dunk. These Republican seats are likely to flip in November even if 2016 turns out to be a surprisingly disappointing year for Democrats. The districts are just too tough for GOP incumbents to hold in any presidential year.

Illinois 10, Bob Dold. Republican Dold is a strong incumbent who fits his district well. But he lost to Brad Schneider (D) in 2012 because of presidential turnout, and he will probably lose in another rematch. Of course, in a midterm with an unpopular Democratic president (like 2018?), don’t bet against Dold. He won in both 2010 and 2014.

Nevada 4, Cresent Hardy. Two years ago, nobody really expected Republican Hardy to win this district, which President Obama carried twice. Given the presidential year turnout and Donald Trump’s rhetoric on immigration, state Sen. Ruben Kihuen should take back this seat back for Democrats.

Shouldn’t need a wave. Even without a wave, these swing districts give Democrats good opportunities. If Democrats lose any of them, Republican strategists will be relieved.

Minnesota 2, John Kline, Open. Republican Jason Lewis won a competitive GOP primary but has so many vulnerabilities that St. Jude Medical executive Angie Craig, the Democratic nominee, has the advantage in this competitive, urban/suburban Twin Cities district.

Nevada 3, Joseph J. Heck, Open. Heck (R) would probably hold this seat for the GOP, but he is running for the Senate. Republican Danny Tarkanian, whose father was a well-known college basketball coach, already has plenty of losses in his resume, but Democrat Jacky Rosen’s appeal is unproven.

Maine 2. Bruce Poliquin. Poliquin upset Democrat Emily Cain in 2014, but this presidential year should help her against the congressman, who has turned into a strong fundraiser and good candidate. On the other hand, it isn’t clear whether Trump will be the drag here that he will be in other parts of the Northeast.

Even a small wave could flip ’em. These seats ought to stay Republican in a neutral year, but even a small partisan wave is likely to turn them blue. Winning these seats alone won’t flip the House, but Democrats need them to fall to have a chance to net 30 seats.

New Jersey 5, Scott Garrett. Garrett usually wins no matter how controversial he is, but the combination of a strong Democratic challenger — former Bill Clinton speechwriter Josh Gottheimer — and a Democratic wave could end the GOP congressman’s career in this expensive, northern New Jersey district.

New York 22, Richard L. Hanna, Open. Moderate Republican Hanna would probably win reelection if he were running again. But if a wave develops, the party will be hard-pressed to hang onto his GOP-tilting district. State Assemblywoman Claudia Tenney and Democratic county legislator/businesswoman Kim Myers will slug it out in November, but independent Martin Babinec could be a factor.

Wisconsin 8, Reid J. Ribble, Open. Ribble’s retirement creates a competitive contest between Republican Mike Gallagher, a Capitol Hill staffer (and former Marine) with expertise in foreign policy, and Outagamie County Executive Tom Nelson, the Democrat. The district is competitive but usually leans Republican. However, a wave could drown Gallagher.

Iowa 3, David Young. Neither incumbent Young nor Democratic challenger Jim Mowrer will set the world on fire, but one of them must win. In a neutral environment, it’s probably Young. With at least a small Democratic wave it could be Mowrer, who lost a congressional race in a neighboring district in 2014.

Savvy GOP incumbents vs. a moderate wave. You know things are getting bad for Republican — and that the House is truly at risk — if these very strong GOP incumbents in difficult districts are losing.

Minnesota 3, Erik Paulsen. Paulsen should win reelection nine out of 10 times in this competitive district. But if Democratic state Sen. Terri Bonoff is able to ride an anti-Trump wave in this Twin Cities district, the House is in play.

Virginia 10, Barbara Comstock. Comstock (R) is plenty savvy, but her Northern Virginia district means that she is vulnerable to an anti-Trump wave. Democrats are hyping their nominee, real estate developer LuAnn Bennett.

New York 24, John Katko. This Syracuse-area seat clearly favors Democrats but can be competitive. Katko is a rising House GOP star, and in a neutral or Republican-leaning year, he should win reelection. But Democratic nominee Colleen Deacon, who worked for the mayor of Syracuse and then Sen. Kirsten Gillibrand (D-N.Y.), should benefit from the district’s bent and hostility to Trump.

Arizona 2, Martha McSally. McSally is a fundraising machine and a GOP star, but her district is very competitive and at least a moderate Democratic wave could give her problems. Democrats will choose their nominee next week: either former state congressman Matt Heinz or state Rep. Victoria Steele.

Tsunami wave upsets only. Given the weak Democratic challengers here, these districts should stay with Republicans. If they don’t, the House probably is in the process of flipping — and a huge Democratic wave is hitting.

California 21, David Valadao. Emilio Huerta, a lawyer, hasn’t put together a good enough campaign to defeat Valadao (R) under normal circumstances.

New York 23, Tom Reed. Retired Naval officer John Plumb, a Democrat, will need a big wave to upset incumbent Reed.

California 49, Darrell Issa. Democrat Doug Applegate had raised $186,000 through the end of June, which is not enough to win this race — unless money doesn’t matter. The former Marine needs a huge wave to upset Issa.