The “Trump rally” — the soaring markets of the year since the 2016 election — was supposed to be largely about taxes. Wall Street believed Republican control of all three branches of government would lead to deregulation and corporate tax cuts — and to increased corporate earnings, higher stock prices, and more money for dividends and stock buybacks that benefit shareholders.

But even though the House of Representatives passed a tax bill Thursday that cuts the corporate tax rate from 35 percent to 20 percent, Wall Street doesn’t seem as excited as you’d expect. Although markets rebounded Thursday, major US equity indexes saw two straight days of declines this week as investors appeared to back away from risk and err more toward caution.

There are two possible explanations: Either investors still aren’t certain that Republican tax efforts will succeed or a tax bill doesn’t matter that much for stock prices.

The stock market is suddenly meh on Congress’s tax bill

The Republican tax plan — which would slash the corporate tax rate and give more favorable treatment to income earned abroad — still faces a big hurdle before becoming law. Getting 50 votes in the Senate isn’t going to be easy.

Under the “budget reconciliation” rules the GOP is using to pass the bill with only 50 votes instead of the usual 60, Republicans can only afford to lose two of its 52 members’ votes.

Sen. Ron Johnson (R-WI) became the first GOP senator to oppose the Senate’s tax bill in its current form on Wednesday. He appeared to hedge his position on Thursday morning, telling CNBC in an interview his “no” could become a “yes” with certain changes. “I want to get this thing fixed,” he said.

Sen. Ron Johnson says he wants to fix the GOP tax bill so he can change his 'no' vote to a 'yes' https://t.co/HFwM2LtPQK — CNBC (@CNBC) November 16, 2017

Wall Street analysts seem to think the plan’s overall chances are good. Goldman Sachs analysts wrote in a note on Tuesday that their odds of tax reform by early 2018 are up to 80 percent from 65 percent as recently as November 8, and said they give a tax bill a 1 in 3 chance of becoming law by year’s end. The Washington, DC-based policy research firm Capital Alpha Partners upped its odds of tax reform to 80 percent from 60 percent and said it’s “most likely” to arrive by the end of 2017.

“The tax reform debate is moving forward faster than we or most other observers expected,” wrote Goldman analyst Alec Phillips.

Phillips in a separate note on Thursday said that recent developments — namely, Johnson’s opposition and a Senate proposal to repeal Obamacare’s individual mandate in its tax bill — have not affected Goldman’s odds on passage.

Stocks moved higher on Thursday, due in part to earnings-driven gains from Cisco and Walmart. But progress on a tax bill hardly has investors euphoric. Either they aren’t buying that the plan is really going to pass or they no longer believe a corporate tax cut is the end-all, be-all for justifying stock prices.

The S&P 500, Dow Jones Industrial Average, and Nasdaq posted declines on Tuesday and Wednesday, swayed by falling oil prices, disappointing data out of China, and a lackluster turnaround plan from the industrials giant General Electric, among other factors. Volatility, an investor fear indicator, spiked as well.

“Even though Goldman upped the likelihood of a tax cut, I think investors are increasingly concerned that it might not happen,” said Sam Stovall, chief investment strategist at the investment research firm CFRA Research, in an email.

This is part of a bigger debate about the stock market and taxes

There’s also a larger debate about how dependent US stock prices are on tax legislation passing in the first place — and how bad it would be for investors if Congress fails to pass a bill. The S&P 500 has rallied about 23 percent, the Dow roughly 30 percent, and Nasdaq approximately 34 percent since the 2016 election.

Treasury Secretary Steven Mnuchin in October warned in an interview with Politico that stocks would see a reversal of a “significant amount” of its post-election gains should a tax bill fail.

“There is no question that the rally in the stock market has baked into it reasonably high expectations of us getting tax cuts and tax reform done,” he said.

But Tony James, president of the private equity giant Blackstone Group, said in an interview with Politico’s Money podcast aired this week that he doesn’t attribute much of the stock market runup to President Donald Trump or think it hinges on tax cuts.

“If we don’t get [tax reform], I think it’s a modest negative for the market,” he said. “But I don’t think it’s a huge driver for the market. I don’t think the market is going to tank by any means.”

The entire capitalized value of the stock market is about $30 trillion, and Republican tax plans entail about $2 trillion in corporate tax cuts, said Steven Rosenthal, a senior fellow at the Tax Policy Center. So while it’s significant, it’s not an enormous chunk of the total market. “It’s going to be hard to tease out the tax effects, the likelihood of taxes going through,” he said.

Corporate earnings have been strong even without a tax bill — third-quarter earnings have come in better than expected, Stovall, the CFRA Research strategist, noted.

Investors might be skittish about tax reform, but they might also be worried it’s just been so long since there’s been a real dip: The S&P 500 hasn’t had more than a 5 percent decline in more than 18 months and hasn’t seen a correction — a reversal of 10 percent or more — since May 2015 to February 2016. US stocks haven’t been in bear territory since the financial crisis.

“I think we are just going through a long-overdue digestion of recent gains,” Stovall said.