By Douglas Heye

(CNN) -- However the special election for Pennsylvania's Congressional District turns out -- and, at this writing, it remains essentially a tie, while absentee ballots are counted -- it represents a major loss for the GOP. It is the latest canary in the coalmine for the party.

As happens after any special election, the losing side will explain what made this race unique and, they hope, an outlier. They do this while throwing their candidate under the bus. We call this spin.

If Rick Saccone, the Republican, wins, it will be nothing near an affirmation of his candidacy. His fundraising lagged, propped up by outside spending, while the fact that he was anti-union in a pro-union, blue-collar part of the state -- where Republicans are typically more friendly to unions -- did not help his case. He just never caught on the way a Republican should in that red district.

If Conor Lamb, the Democrat, wins, his particular candidacy can hardly be seen as the portent his party would like. Few Democratic congressional nominees in the midterms will resemble Conor Lamb, who proved to be what Democrats had hoped failed Georgia special election candidate Jon Ossoff would be. Campaigning in part against Nancy Pelosi practically makes Lamb a unicorn in -- and perhaps future model for -- today's Democratic Party.

Indeed, Lamb more resembles the "backwards" kind of voter that Hillary Clinton blamed for her loss in places like PA-18 than the average member of the current House Democratic Caucus.

But a Saccone loss in a district overwhelmingly carried by President Donald Trump -- even a district that, due to court-ordered redistricting, will soon disappear (a congressional Brigadoon) -- would begin and end with massive voter disapproval of Trump.

Indeed, putting the race strictly in terms of the district and the candidates would ignore the national political winds as surely as the Democrats did in early 2010. They sought to insulate Barack Obama from criticism and blamed Democrat Martha Coakley's loss in a special election in Massachusetts on a "bad" candidate losing to the "good" GOP candidate, Scott Brown.

Trump's national approval rating, depending on which poll you look at, generally ranges from 38-42% -- numbers so far in the cellar that they should cause genuine fear to Republicans, who hope to keep the House. This is mirrored in states he won, where he is under water, as well as in states Hillary Clinton won handily, such as California, New Jersey and New York, where there are a lot of vulnerable seats in the fall.

At the Republican National Committee in 2010, our "magic number" for President Obama was 46%. If his approval was below that, we believed we would win back the House. It was, and we did, netting a total of 63 House seats.

With Trump's numbers well below that, and the open question of whether the Trump voter shows up for midterm elections, a mirror image of the problem Obama faced is a very real one for Republicans. This talk is serious in and of itself, but it is significant to note how early this conversation began. At the Republican National Committee in 2010, we didn't see winning the House as a serious possibility until after Labor Day. Neither did the Democrats in 2006, when they won the House. The difference in 2018? Trump.

We've already seen how this environment is manifesting itself within the GOP. Many lawmakers are simply throwing in the towel and retiring. Close to 40 House Republicans -- including 8 committee chairs -- have already announced their retirement, compared with only 16 Democrats. With a 25-seat majority -- and an average midyear loss to the party in power is 24 -- there is little room for error.

In a perfect world, there should be plenty for Republicans to campaign on. Job growth and wage growth remain strong. The Republican tax bill continues to grow in popularity, aided by positive headlines touting bonuses and raises tied to the bill in congressional districts throughout the country. The economy is strong.

And yet, the Pennsylvania special election -- its outcome still on a razor's edge -- shows it's not merely "purple districts" or "Hillary Districts" at risk for Republicans, but even some solidly red districts. It bears repeating: a Republican candidate in a district Trump carried by 20 points is struggling at the finish line. To torture Frank Sinatra's most famous lyric, if it can happen there (or in an Alabama Senate race), it can happen anywhere.

In the meantime, while Republicans face 32 competitive races this fall, keep an eye on potential Republican retirements. If we continue to see more, members may look more like animals scurrying ahead of an earthquake they feel hitting their district before anyone else.