There is no way for Republicans to sugarcoat what happened in southwestern Pennsylvania on Tuesday. It’s true that campaigns and candidates matter, but fundamentals often matter more. That’s why Republicans should be nervous about November.

The special election in Pennsylvania isn’t the first data point to show Republicans that they’re in trouble, but if there was any complacency among elected officials, that’s certainly gone now. The all-but-final counts in the congressional race have left Democrat Conor Lamb marginally ahead of Republican Rick Saccone in a district that Donald Trump carried by 20 points in 2016 and that Mitt Romney carried by 17 points in 2012.

The message was clear. In this election cycle, Trump is a great motivator for Democrats, who still feel the sting of the 2016 election and are eager to vote in opposition to the president. Nowhere does this appear more evident than in suburban precincts nationwide, as the counts from the suburban Pittsburgh sections of the district showed on Tuesday night.

Taking back the House is no slam dunk for the Democrats. They still lack a clear, positive and unifying message, just as they did in 2016. But in the nuts-and-bolts category, more than enough Republican seats are at risk for strategists on both sides to see a path toward a Democratic-controlled House starting in January.

Republicans probably will have to consider developing a defensive strategy aimed at checkmating Democrats from picking up the 24 seats needed to take control of the chamber, rather than expecting the underlying dynamics of this election year to change significantly between now and November.

Tuesday’s contest was a special House election like few others, held in a district that will soon cease to exist, because of new boundaries in Pennsylvania that will govern the November elections. So the vanishing 18th Congressional District went out in grand style Tuesday, with a down-to-the-wire contest that kept political aficionados on edge all night waiting for a decisive outcome. For pure theater, it exceeded expectations by a mile.

With Democrats eyeing the 2018 elections as a chance for a blue wave, here's how they're fighting to win the 24 seats they need to take control of the House. (Jenny Starrs/The Washington Post)

In the heat of the moment, as the margin between Lamb and Saccone shifted with every update, some Republicans sought solace in what they were seeing. Many had dismissed Saccone as a weak and ineffective candidate. That he fought the more charismatic Lamb roughly to a draw after strategists on both sides headed into Election Day believing that the Democrat would win by several percentage points gave some Republicans a false sense that things might not be as bad this fall as feared.

Republicans with longer-term horizons were not blinded by temporal events. They know how challenging the climate is for their party. There is the historical reality that the party in the White House loses ground in the first midterm contest after a president is elected. There is the fact that Trump is a divisive leader with approval ratings in dangerous territory. And there is evidence that the Trump coalition, like that of president Barack Obama, is not necessarily a transferrable asset. Republican candidates must shoulder the burdens of this presidency without necessarily enjoying the benefits.

Although Tuesday’s outcome is only one case and therefore limited for analysis, the first test of Republicans’ hopes of making the economy and their new tax bill focal points of this year’s elections fell far short. Whatever voters think of the tax bill, the issue did not appear to give any significant electoral boost. Perhaps by November, with persistent effort, that could change. But nervous Republicans probably will be looking to test additional messages to offset the anti-Trump sentiment driving many voters.

The Cook Political Report now lists 47 Republican-held districts in some form of jeopardy — classified as toss-ups, leaning Republican, leaning Democrat and in one case likely to be won by Democrats. An additional 27 GOP seats are on the watch list, considered likely retentions at this moment. By way of contrast, there are just eight Democratic seats listed as either toss-ups or leaning in the Democrats’ direction. Eleven other seats bear watching, according to the Cook team’s analysis.

The Cook analysis rates each district along an ideological scale. The Pennsylvania district showed a Republican lean of plus-11. More than 100 districts nationwide are roughly equal to or far less Republican in their ideological leanings. Not all of them will be competitive in November, but what Pennsylvania highlighted is that with the right combination of ingredients, particularly in districts without an incumbent in the race, Democrats can be competitive.

Although fundamentals will guide the outcome of most races in November, candidates will make a difference. In Pennsylvania, Lamb fit the cultural and political leanings of the district. He ran away from House Minority Leader Nancy Pelosi (D-Calif.). He embraced the Second Amendment in a part of the country that Obama described — in one of his biggest gaffes of the 2008 campaign — as populated with people who “cling to guns and religion.” Lamb also endorsed Trump’s new tariffs on imported steel and aluminum, which put him in harmony with union voters in the district who supported Trump in 2016.

The Democrats will have to navigate this challenge of finding candidates who fit their districts in upcoming primaries. The balance of power in the party has shifted toward the progressive wing, which could affect intraparty contests in districts that are more centrist or conservative. Republicans will look to exploit any such mismatches in November and are talking about how to influence the Democratic primaries in this way.

The president plans to be an active campaigner this fall. Republicans think his Saturday night visit to Pennsylvania provided a shot of energy that helped Saccone narrow what was considered Lamb’s preelection poll advantage. But Trump’s reach will be limited. With several dozen competitive House races come October, Trump will be able to campaign only in a relative few in the final weeks. The White House political team, in conjunction with congressional leaders and party strategists, will have to pick carefully to maximize his impact.

As the vote counting seesawed Tuesday night, many Democrats were ready to claim a victory even if Lamb were to lose. But there will be no moral victories in November. Either Democrats will take back the House or they won’t. A narrower Republican majority is likely, but only a Democratic takeover would truly upend the balance of power in Trump’s Washington.

Based on Tuesday night, along with Democrat Ralph Northam’s gubernatorial victory in Virginia in November and the coalition that helped elect Democrat Doug Jones of Alabama to the Senate in December, a consistent pattern is taking shape — that of an energized, Democratic grass-roots base battling a conflicted Republican Party. It’s doubtful that Republicans need any more examples to prepare them for what’s to come.