The special House election in Pennsylvania's 18th congressional district was, among other things, a test of political messaging going into the 2018 midterms. It did not go well for Republicans. Democrat Conor Lamb declared victory early Wednesday. Though he held a lead of just under 700 votes, NBC News projected him the winner.

Outside Republican groups dumped $10.7 million into the race to help Republican Rick Saccone, but the GOP groups "backed away from their signature tax-cut law in the final days" and weeks of the campaign, focusing their ads instead on "so-called sanctuary cities and attacking Democrat Conor Lamb's record as a prosecutor," Politico reports. "The strategy shift has been dramatic," Politico documents, explaining why it matters:

If the tax law isn't a reliable vote-winner, it means Republicans may have to find different midterm messaging to go along with a consistent wave of attacks linking Democratic candidates to House Minority Leader Nancy Pelosi. The Pennsylvania race will mark the second major contest of the cycle, following the Virginia governor's race, where Republicans abandoned a tax cut-focused message to hammer a Democrat over immigration and crime. [Politico]

President Trump won the district by 20 points in 2016, and "there are 114 Republican-held House seats more competitive than Pennsylvania's 18th," NBC News reports.

"If this race is reflective of the messages from the two parties going into November, Republicans have trouble on their hands," says Chris Stirewalt at Fox News. "The conventional wisdom in Washington was that the key to midterm survival for Republicans is to focus on the booming national economy and the role of the GOP in making it that way," but "how do you tell people in the same breath that your policies are working, but that America is teetering on the brink of failure? If peace and prosperity aren't good enough to run on, what would be?" Peter Weber