The most dangerous outcome for Republicans in Tuesday's special House election was not the prospect of a Democrat taking over one of their seats.
It was the shrugging off by voters of the party's biggest legislative achievement: the tax cut measure that Republicans hoped would be their major campaign message as they head toward a turbulent midterm election.
Though the popularity of Trump's tax plan has grown since it was passed last year, it stalled as an election issue in Pennsylvania, leading Republicans to shift away from it late in the campaign in search of another topic to energize supporters of state legislator Rick Saccone.
"It looks like it just petered out," pollster Patrick Murray of the nonpartisan Monmouth University Polling Institute said of the tax plan's impact on the election.
Democrat Conor Lamb held a narrow lead over Saccone on Wednesday, although the ballot count was not final. Win or lose, Lamb's showing marked a dramatic improvement for Democrats in a district Trump seized by almost 20 percentage points in 2016.
Although one well-connected Republican characterized the private response by his party as a "freak-out," party leaders publicly did not question whether they had overestimated the impact of the issue that is almost certain to be the GOP's biggest calling card as it tries to retain control of Congress in November.
Speaking to reporters Wednesday, House Speaker Paul D. Ryan (R-Wis.) played down Lamb's showing on the grounds that he ran as a conservative Democrat. Unmentioned by the speaker: Lamb campaigned against the tax plan.
"We need to execute, we need to get our message, we need to make sure that our candidates aren't massively out-raised and outspent on TV as was the case between these two candidates," Ryan added.
Counting outside spending, however, Republicans actually dumped more resources into the race, leading some to blame Saccone rather than the difficulties facing the party.
"Campaigns and candidates matter," said Matt Gorman, a spokesman for the National Republican Congressional Committee, which works to elect GOP House members.
"If you can't get your message out," Gorman said, "then you don't have a message."
The election in the Pittsburgh area, to replace a Republican incumbent who resigned in disgrace, was of limited utility; the district has already been gutted in a redrawing of congressional lines by the state Supreme Court, so the winner will have to run elsewhere in November.
But coming in the spring of an election year that already appears to be a stiff climb for Republicans, the race offered another look at the political potency of a nationally unpopular president whose presence in the White House has fanned unprecedented levels of Democratic enthusiasm.
Democrats already were riding successful efforts at the end of 2017 in a host of Virginia races and the contest for a U.S. Senate seat in Alabama.
Several Republicans fiercely disputed the notion that Tuesday's results showed that there were limits to the political impact of the tax cut plan.
Corry Bliss directed an outside effort working on Saccone's behalf that ran multiple ads citing the tax cut plan and trying to link Lamb to Democratic leader Nancy Pelosi of San Francisco. He said that regardless of Tuesday's results, he sees both topics as beneficial to Republican candidates.
"If I could sign a deal … with Democrats that the only two things we talk about are the tax plan and Nancy Pelosi, I would do that in a second," Bliss said.
The closing days of the Pennsylvania campaign, however, showed evidence of ambivalence. Saccone continued to talk about taxes; on Monday he and Donald Trump Jr. arrived at a candy shop in the district to tout fiscal benefits to the store and its workers as a result of the tax measure.
During a Fox News appearance Tuesday morning, Saccone returned to the topic.
"Every day it seems people are still coming up to me, telling me how it's benefiting them — single moms and small businesses that are expanding," he said.
But groups airing ads to benefit Saccone steered many of their pitches onto more visceral turf in the closing weeks of the campaign, a sign that they were searching for more-potent messages.
Typical was a National Republican Congressional Committee ad that struck at Lamb's tenure as an assistant U.S. attorney.
"Liberal Conor Lamb cut multiple plea deals and the gunrunners walked back on the streets," the narrator intoned. "They placed firearms into the hands of criminals and Conor Lamb let them run free. We just can't trust Conor Lamb to keep our families safe."
Neither preelection polls nor Tuesday's results showed the tax plan to have a magnetic hold on voters.
Murray noted that in a Monmouth poll published last week — after respondents would have begun seeing the impact of the tax cut bill on their paychecks — only 23% of Americans surveyed expected their taxes would drop as a result of the law. Even among Republicans polled, only 35% expected to see a tax break emanating from a measure pushed by their own party's lawmakers and president.
Those numbers, Murray said, spoke to the skepticism of voters who, even if they might see some benefit themselves, were disgruntled by the fact that corporations and the wealthy benefited more.
"The public doesn't look at its absolute return," he said. "It looks at relative return — not just 'Am I getting my fair share?' but 'Is someone else getting more?'"
Republicans in Washington have been relentless about touting the tax measure. At their weekly meetings with reporters, GOP leaders have marched one by one to the microphone to tell of their district visits to giant home improvement stores and small businesses, recounting stories of voters who said their prospects had been boosted as a result of the new law.
Last week, Rep. Cathy McMorris Rodgers (R-Wash.) ticked off a series of optimistic indicators of business growth and boosts in jobs, crediting the tax plan.
She introduced Rep. Karen Handel, the Republican winner in a hard-fought Georgia race last year, who talked of her conversations with women in the construction industry who had attested to the benefits of the tax plan. One woman, Handel said, was bringing home an extra $260 a month.
"That is meaningful and real for a single mom making sure that her daughter gets through college," Handel said. "This is working for Americans, it's working for women, it's working for most working families across this country. And I look forward to seeing more positive results in the months to come."
But several people looking at the 2018 races suggested that several factors weighed against the GOP tax cuts developing enough strength to cut into the Democratic advantage this year.
Trump is the election's animating force, for one thing, overshadowing any specific issue and even the candidates. The president held a Saturday night rally in Pennsylvania that was ostensibly to boost Saccone, although the candidate was only minimally mentioned.
Even before Trump's election, the political environment had grown bracingly partisan; the antagonism between the sides is believed by many to limit the impact of any one issue in turning public opinion among voters who side with their self-selected partisans.
Trump won in places such as Pennsylvania in 2016 with a sharp message playing to voters' anxiety about being displaced in modern-day America. Robert Jones, chief executive of PRRI, which conducts regular polls on national politics, said it was not clear that a more prosaic message about tax savings would have the same heft.
"Something like an extra 100 bucks in my tax return — I don't think it's going to stand up very well against 'The immigrants are coming for my job and ISIS is coming for my children,'" he said. "Those messages are much more powerful."
9 a.m.: This article updated with comments from House Speaker Paul D. Ryan (R-Wis.).