MIAMI — A dozen high school students working for Americans for Prosperity, the conservative political network funded by Charles G. and David H. Koch, fanned out across the Little Havana neighborhood one day last week to make the case that the Republican tax bill was something to get excited about.
“We believe it’s time to fix our broken tax code and let families keep more of what they earn,” Barbara D’Ambrosio, a sophomore, dutifully told an elderly woman who answered the door in her slippers. After she finished her script, Barbara glanced up from the iPad she was carrying and asked if the woman would kindly call her senators to urge them to support the tax bill, which was hours away from being approved by the Senate.
The woman stared at her silently for a moment. Then she nodded, politely but unconvincingly.
So Ms. D’Ambrosio and her friends soldiered on, visiting about 40 houses that afternoon and finding more of the same: people who were often unenthusiastic, unaware or simply uninterested.
It’s the trickle down theory of selling tax cuts to the American voter. Conservative activist groups like Americans for Prosperity, celebrating what they expect is the imminent passage of a tax package that they and the Republican Party’s corporate backers have sought for a generation, now need to convince ordinary Americans that this is good for them too.
These groups have marshaled their resources in almost every state in a campaign that can sound at times as if it were something a Democrat dreamed up, complete with tributes to the American worker and the middle class.
“The American people have waited 31 long years to see our broken tax code overhauled,” the leaders of the Koch’s political network insisted in a letter to members of Congress on Monday, urging swift approval of final legislation. They added that the time had come to put “more money in the pockets of American families.”
The problem, as Republicans are learning, is that most Americans do not believe that is what the tax plan will do.
Steve Schmidt, a Republican strategist, said that amid all the talk about the need to score an important victory for their party, “it bears mentioning that the ‘win’ is something that is extraordinarily unpopular with 75 percent of the American people.”
The tax proposal seems ill-fitting for the mood on the right, perhaps explaining some of the skepticism. It would add $1 trillion to the deficit, according to the official congressional scorekeeper, contradicting the calls for fiscal austerity that conservatives made for years under President Barack Obama. And its generosity to corporations and the wealthiest Americans is at odds with the soak-the-rich economic populism President Trump preached during his campaign.
But for groups like the U.S. Chamber of Commerce, those in the Koch’s vast network and others closely aligned with the pro-business wing of the Republican Party, the tax bill would be the only tangible legislative achievement after 11 months of an uneasy and, so far, unproductive alliance with a president they fiercely resisted during last year’s election.
The legislation is among the most unpopular public policy initiatives taken up by Congress in recent years, polling shows. A variety of factors is compounding that, Republicans say, from its complexity, to the secrecy and hurriedness of the process to the perception that the benefits will flow largely to a select few.
“We Republicans get into the weeds and talk about technical tax policy and the budget process, and for the average American, that ends up sounding like the adults on the old Charlie Brown cartoon — wah, wah, wah,” said David McIntosh, president of the Club for Growth, which has been among the groups pushing for tax cuts. “And the Democrats are messaging: ‘This is not fair to the middle class and the poor.’”
Ken Spain, a Republican consultant who works on financial and tax issues, said the legislation has become “a blank canvas” for the opposition to paint and that his party is to blame.
“There hasn’t been a cohesive messaging strategy to date, and the polling data reflects that,” he added.
Americans also see the tax bill as inextricably linked to the Republican Party and Mr. Trump. And majorities of the country deeply disapprove of both.
In many public polls, Americans see the Republican tax plan in a more negative light than they did the Affordable Care Act before it became law in 2010. Never overwhelmingly popular, opinion on the health care law was generally evenly split at that time.
But the discontent runs deeper than an affinity for one party over the other. Not only do a majority of Americans doubt it is good policy, but people in conservative areas of the country have low expectations that it would do anything to help them, new polling has found.
In counties where Mr. Trump performed exceptionally well — that he won but Mr. Obama carried in 2012, or where he ran 20 percent ahead of what Mitt Romney received in 2012 — only 17 percent said they expect to pay less in taxes, according to a recent NBC News/Wall Street Journal poll. Another 25 percent said they expected their family would actually pay higher taxes.
Those numbers were similar to a recent Quinnipiac poll that found 59 percent of voters believe the Republican tax plan favors the rich at the expense of the middle class.
Peter D. Hart, the Democratic pollster who helped conduct the NBC/Journal poll, called the tax cut package “penthouse populism” that risked tarnishing Mr. Trump’s image with those who see him as a “drain the swamp” crusader fighting powerful and entrenched interests. “The swamp isn’t only Washington to them,” Mr. Hart added, “it’s Wall Street. It’s the wealthy.”
Given the lack of public appetite, Republicans and the conservative groups working to shift attitudes on the tax proposal have had to fine tune their messages. Mr. Trump and White House officials, for example, used to often highlight how the tax cuts would spur an uptick in growth.
“Grand economic arguments don’t matter,” said Corry Bliss, executive director of the American Action Network, a conservative group that works closely with Republican leaders in Congress. “What became clear is that to connect with voters you have to explain what is best for them,” Mr. Bliss added, noting that voter cynicism and mistrust in politics has become increasingly difficult to overcome, even with the strongest messaging.
“When we say, ‘This is going to create 8 million jobs,’ people don’t believe it. And they don’t care. They care about one job: their job.”
The American Action Network, among the largest groups helping lead the effort to sell the tax plan, has committed $22 million to running television ads in English and Spanish. One is a new commercial that ran in California, Texas, Florida and Virginia in which a man says in Spanish, “Congress, a simpler, fairer tax code means more opportunity for working families.”
Americans for Prosperity and its field staff and volunteers have hit more than 41,000 homes and made 1.1 million phone calls. In all, the Koch groups have spent $10 million on events, grass roots canvassing and advertising. In Little Havana late last week, the high school students — for whom the canvassing worked toward their community service requirements for graduation — were leaving bright orange door hangers behind on each home they visited.
“Unrig the Economy,” the signs said, listing the various purported benefits of tax reform: “Improve Lives/Leave More Money in Your Pocket/Create Stronger Job Growth.”
Sometimes it can be hard to tell if they are making much progress. Enoch Jean-Mary, a junior, said that when he has made phone calls lately, only about two of every ten people he reaches agree to take a survey on tax reform.
But Starla Brown, the Americans for Prosperity Florida grass roots director, insisted she was seeing real enthusiasm. When she spoke to a group of Florida State University students recently, she said, “There was resounding applause when I brought up tax reform, which was a surprise.”
After their canvassing ended and the students piled into the back of Ms. Brown’s S.U.V., she started flipping through the channels on her satellite radio, hoping to find an update on the looming Senate vote. The students sat behind her, talking not about taxes but the new iPhone.