For months, Sen. Marco Rubio has taken shots at the GOP tax plan, essentially arguing it's stacked for the rich. And for months the Florida Republican has blanketed TV news and given speeches in favor of expanding the child tax credit, casting it as an investment in hard-working families.

"There was a time when the American worker was a hero in our country and people looked up to the American worker and idealized it," Rubio said Tuesday on the Senate floor.

The Senate tax bill, primed for a vote Friday, would double the current $1,000 per-child tax credit. Still, it gives scant relief to the struggling workers Rubio talked about while affording benefits for more well-off families.

Despite his stand, Rubio was expected to vote for the overall bill. He and other advocates succeeded in getting Senate tax writers to bump the credit to $2,000. It wouldn't do much for lower-income families — 10 million would get $75 or less — and so, Rubio pushed to make it refundable against payroll taxes. He also wanted the credit to grow with inflation.

Wednesday, Rubio and Sen. Mike Lee, R-Utah, proposed paying for a more generous credit by taking some away from corporations, dropping the current 35 percent rate to 22 percent instead of 20 percent. The White House quickly dismissed the idea and influential voices piled on, one suggesting Rubio took a populist stand with an eye on competing again for president.

"Mr. Rubio may be setting himself up to run as a social conservative hero in 2024, or even 2020 if President Trump declines to run, and the child credit obsession is a down payment on that brand," read a blistering Wall Street Journal editorial. "Yet voters looking for a candidate who understands what makes America—and American families—prosper will have to look elsewhere."

Others defended Rubio. "Folks, at a time of declining birth rates in America, if we are going to use the tax code to incentivize behaviors (we should not, but it does and that's reality), promoting children and families should be a chief goal of the tax code," wrote conservative blogger Erick Erickson.

Rubio, a father of four who has long emphasized his parents' working-class story, scoffed at the criticism. "For years everyone including myself touted a corporate tax cut down to 25 percent as pro-growth. But suddenly 20 percent is the new magic number."

Senators are expected to vote on Rubio and Lee's amendment on Friday — the chances of it passing are iffy — before taking up the overall package.

Rubio and Lee first teamed up on the child tax credit in 2015 and then said it should be increased to $2,500. They won a high-profile ally after the presidential election: Ivanka Trump. The House tax proposal called for $1,600 and the Senate added a mere $50 to that before going to $2,000, costing an additional $13 billion per year.

Sen. Tim Scott (R-S.C.), Ivanka Trump, and Sen. Marco Rubio (R-Fla.) at a news conference regarding tax policy, on Capitol Hill in Washington on Oct. 25, [Gabriella Demczuk/The New York Times]
Sen. Tim Scott (R-S.C.), Ivanka Trump, and Sen. Marco Rubio (R-Fla.) at a news conference regarding tax policy, on Capitol Hill in Washington on Oct. 25, [Gabriella Demczuk/The New York Times]
On one level, $2,000 per child is a victory for Rubio and it will help 3.5 million families avoid tax increases driven by the overall legislation, according to an analysis by the New York Times, which notes the middle class tax cuts have an expiration date of 2025. At the same time, it provides another boon to the wealthy by raising the full eligibility level to those earning up to $1 million.

The working class gets relatively little and millions who do not pay income tax would be left out. An analysis by the left-leaning Center on Budget and Policy Priorities estimated that more that more than 30 percent of children in nearly all states would receive less than the full increase and in 15 states, Florida included, at least 45 percent of children would be shorted. (The plan also makes undocumented immigrants ineligible for the tax credit, a blow to people in states such as Florida with a large immigrant population.)

Rubio and Lee took to the Senate floor on Wednesday and held up the stories of waitresses, truck drivers, firefighters and nurses, who wouldn't get much help. "These are working people, the backbone of our country, the ones who have been left behind for over three decades because no one fights for them," Rubio said.

Democrats have pushed for an even higher child tax credit and blamed Republicans for shutting them out of discussions. Florida Democratic Sen. Bill Nelson called the GOP tax credit "nibbling around the edges" as he blasted the overall $1.5 trillion tax package as a boon for the rich.

"Nothing about it is fair," Nelson said in an interview.

Protesters in front of Rubio's office in Doral on Sunday. [Joe Raedle/Getty Images]
Protesters in front of Rubio’s office in Doral on Sunday. [Joe Raedle/Getty Images]
Nelson did manage to get something in the bill, with an assist from Republican Sen. John Cornyn of Texas, who co-sponsored an amendment to give citrus growers a deduction for new trees replacing those savaged by greening disease. But it’s a blip — $30 million over a decade — in the overall package that Nelson and all other Democrats oppose.

Some Republicans had been reluctant to back the legislation given its dramatic impact on the deficit. Rubio himself first ran for Senate in 2010 with alarms about the level of debt. But he argued in an October interview with the Tampa Bay Times and other reporters — part of his effort to sell the child tax credit — that the cuts would spur economic growth.

"That's the only way to bring debt under control," he said, "growth and fiscal discipline on your spending side."

He has also argued that non-discretionary spending has to come under control and pointed to "responsibly" restructuring Social Security and Medicare.