By the end of the day, Republicans are pretty sure they will have passed a historic tax overhaul that could save their imperiled majorities in Congress.

And Democrats are pretty sure that Republicans just signed their political death certificate. To wit: There are 10 Senate Democrats running for re-election in states President Donald Trump won last year. Not a single one voted for the tax bill. In fact, a number of them vociferously opposed it.

"Instead of providing a tax cut that overwhelmingly benefits the middle class, this bill cuts taxes for the wealthiest Americans while raising taxes on a majority of families making less than $75,000 in the coming years," Sen. Joe Donnelly, D-Ind., said on the Senate floor Tuesday.

Donnelly is one of the most endangered Senate Democrats up for re-election next November, given that Trump won his state in the 2016 election by 19 points. And yet he has decided it's good politics to oppose a tax overhaul that Trump will champion.

Other Democratic senators in deep-red Trump states also telegraphed to constituents that they don't like this bill.

"Shortsighted and rushed," Sen. Joe Manchin III, D-W.Va., said. He's attempting to win re-election in a state Trump won by more than 40 percentage points. Sen. Claire McCaskill, D-Mo., who is currently one of the most endangered senators of either party in next year's elections, said: "This tax plan doesn't live up the commitment I got from President Trump, when he told me he wouldn't support tax reform that benefited the very rich at the expense of the little guy."

As McCaskill's statement indicates, these Democratic senators clearly see the political value of appearing to work with Trump. They accepted the president's invitation this fall to dine and talk about taxes, and many of them would have loved to sign a bipartisan bill that could let them claim they are working with the president.

But Democrats have calculated that a mix of public perception and the popularity of populism has made this bill toxic to voters. They are convinced that cutting taxes for the wealthy and corporations while giving the middle class a temporary tax cut strikes the wrong tone. And polls suggest Democrats are right. Polls consistently show that only about a third the country supports the bill, while two-thirds think it will mainly benefit the wealthy.

The Manchins and McCaskills and Donnellys of the world are also likely very aware of this stat: 43 percent of Americans say they are less likely to vote for a lawmaker who supported the plan, a recent Quinnipiac Poll found. A separate Quinnipiac Poll released Tuesday found that more than half of Americans say they want Democrats to control Congress, and that half of Americans disapprove of the way Trump is handling the economy.

In other words, Republicans are going to have to do some major convincing — and hope their unproven theory of trickle-down economics works — if they want to campaign successfully on this tax bill.

Democrats running in Trump country aren't taking that bet. In fact, it was an easy choice for them to oppose the bill, their operatives say. "When you have an unpopular president selling an unpopular bill, it doesn't create political pressure to fall in line and support it," said Democratic operative Jesse Ferguson. Democrats' Senate campaign committee, which suddenly has a path to take back control of the chamber next year, has already released ads in six states attacking Republicans who supported the tax plan.

Republicans have argued that Americans just have the wrong idea about this bill, warped by Democrats and negative media coverage. "Results are going to make this popular," House Speaker Paul Ryan, R-Wis., declared Tuesday.

People won't file their taxes under this new code until after the November 2018 midterm election. But as employers start to adjust how much in taxes they take out of people's paychecks, it's possible Americans could see a slight increase in their take-home pay in a few months.

Senate Republican operatives think they can go on the offensive against Democrats who opposed this bill. America Rising, an outside group that specializes in getting dirt on Democrats, said they're going to frame Senate Democrats' opposition as a partisan move designed to hobble Trump. "Senate Democrats like Claire McCaskill chose internal Democratic politics over boosting the economy of their states and allowing middle-class families to keep more of their hard-earned paychecks," said Scott Sloofman, press secretary for America Rising.

So, who's right? The closest comparison we have to whether Republicans are putting themselves in political danger with this bill is the Affordable Care Act. When Democrats unilaterally reformed the health-care system in 2010, it was unpopular, and they suffered massive defeats in the next election. Democrats lost 63 seats in the House and have yet to regain the majority. But ACA was 10 to 20 percentage points more popular then than this tax bill is today.

Only time will tell whether Republicans are signing their political death certificate with this bill. But it's notable that Democrats in Trump country certainly think so.