The strategy shift has been dramatic.

For the weeks of Feb. 4 and Feb. 11, roughly two-thirds of the broadcast television ads from Saccone’s campaign, the Congressional Leadership Fund super PAC and the National Republican Congressional Committee mentioned taxes, according to a POLITICO analysis of data from Advertising Analytics. For the week of Feb. 18, that dropped to 36 percent, and to 14 percent the week after. Since the beginning of March, tax ads have been essentially nonexistent. Only two are on the air now — a TV ad from America First Action, a pro-President Donald Trump super PAC that briefly mentions the tax law, and a radio ad from a progressive group attacking Saccone for supporting the law.

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.

GOP strategists working on the race scoff at the idea they are abandoning tax cuts as a driving message in the election, noting that Republicans are advertising on the issue online and in mailers. “If the Democrats are willing to sign a deal that the only things we’re allowed to argue about for the midterms are the tax cuts and Nancy Pelosi, show me the deal. I’ll sign it right now,” said Corry Bliss, executive director of the Congressional Leadership Fund.

But other Republicans are beginning to wonder whether the GOP needs to add to its midterm messaging.

“We haven’t looked at the polling they’ve undoubtedly looked at in deciding how to craft their message,” said Club for Growth President David McIntosh, asked by a POLITICO reporter about the strategy shift away from tax reform ads and toward cultural issues on C-SPAN’s “Newsmakers.” “They’ve clearly looked at it and said these messages are the ones more likely to help Saccone win.”

McIntosh, a former congressman from Indiana, said the GOP needs a more forward-looking agenda to build on the tax cuts. “You don’t win elections on what you did in the past,” he said. “I think most voters will say, ‘Good, thank you. What you are going to do next?’”

Democrats, meanwhile, are pointing to the new ads, along with new national polling, to argue the tax law won’t be the life preserver to save the Republican Party’s sinking midterm hopes.

“If the panacea for Republicans’ midterm woes isn’t working in a district that Trump won by 20 points, how is it supposed to save them in battleground districts that are far more competitive?” asked Jesse Ferguson, a Democratic strategist who ran the Democratic Congressional Campaign Committee’s independent-expenditure arm in 2014. “The tax bill isn’t a bulwark. It’s backfiring.”

Lamb and Saccone are running in Pennsylvania’s 18th District, which includes the more educated suburbs of Pittsburgh and working-class exurbs and rural areas. Unlike previous special elections this cycle, which were triggered by Trump’s Cabinet appointments, this seat came open when then-Rep. Tim Murphy (R-Pa.) resigned after revelations that he pressured a woman with whom he was having an affair to have an abortion.

Days before his group aired its first ads in the race, Bliss wrote a memo arguing the tax fight would be the signature issue of the midterms in January. “There is no positive outcome in November if we do not show that we cut taxes for the middle class,” he wrote in January. But his super PAC has stopped airing ads about the tax cuts.

“The mission right now is base turnout,” he said, explaining why his group’s ads have gone from single mothers touting how the tax law helps them to attack ads on sanctuary cities and suggesting Lamb went easy on gun runners while serving as a local prosecutor.

While the Lamb campaign decided to rebut GOP attacks linking him to Pelosi (D-Calif.) with an ad reminding voters he’s promised not to support her, the only cover he’s received on taxes has come in the form of a radio ad from the liberal group Not One Penny.

“Rick Saccone and his friends are flooding the airwaves with negative ads about taxes, but he never mentions how his tax plan hurts Western Pennsylvanians,” a male narrator says in the 60-second ad. “Because 83 percent of the new tax cuts go to the wealthiest 1 percent, while people who have to work for a living pay more.”

The tax plan included large cuts to the corporate tax rate, while also including 10 years of income tax cuts that will lower the tax bills for the majority of Americans and adding a projected $1.5 trillion to the deficit.

There are other signs the tax law may not have the vote-moving power Republicans are counting on. After support for the changes to the tax code rose following the law’s enactment late last year, polls show the percentage of voters who approve of the law has stagnated. A Quinnipiac University poll released last week found that just 36 percent of registered voters supported the law, while 50 percent opposed it. And a poll from Monmouth University, which had earlier showed a narrow plurality approving of the law, showed support dropping to 41 percent of registered voters, with 42 percent opposition.

And even in surveys that show greater support for the law than other polls, like the POLITICO/Morning Consult poll, few voters report seeing more money in their paychecks this year as a result of changes to the tax code.

Back in Pennsylvania, voters are aware Lamb doesn’t support the tax law, according to private polling from a Republican group. In late February, 48 percent of likely voters said Lamb didn’t support “middle-class tax cuts,” while 35 percent said he did.

But messaging on Pelosi — the other key element of the GOP’s midterm strategy — appeared more effective. In January, only 45 percent of likely voters thought Lamb backed Pelosi. By late February, that had jumped to 57 percent. (Soon afterward, Lamb began airing ads where he promised not to vote for Pelosi.)