National Economic Director Gary Cohn, left, accompanied by Treasury Secretary Steve Mnuchin, speaks at the White House on April 26, 2017, where they discussed President Donald Trump tax proposals. (AP Photo/Andrew Harnik) (Andrew Harnik/AP)

Wall Street bankers and investors are ratcheting back their already faded expectations for Republicans to deliver wins that turbocharge the economy after a week of turmoil in the nation’s capital that whipsawed markets.

Those seeking an economic lift from one-party Republican control of Washington in the form of a tax code rewrite and decreased financial regulations — along with a hefty dose of infrastructure spending — are becoming increasingly skeptical. The markets tumbled last week — while recovering much of that ground by Friday — as one bombshell report after another emerged about the Trump administration’s relationship with Russia.

The news that former FBI director Robert S. Mueller III was appointed special counsel by the Justice Department to probe alleged Kremlin meddling in the election, along with possible ties between Trump officials and Russia, did not assuage fears on Wall Street that the Trump economic agenda is on life support, for now.

“With the distractions building in Washington, we’re becoming that much more convinced of the challenges to getting major policy implemented,” said Michelle Meyer, chief U.S. economist for Bank of America, adding the bank hasn’t officially changed its forecast “because events are moving so quickly.”

“The political outlook has changed considerably over the last couple of weeks,” Goldman Sachs analyst Alec Phillips wrote in a Friday note to clients. In part because the investigation into Russia’s alleged meddling in the election and Trump aides’ suspected Russia ties has “clearly escalated,” he downgraded the chances for any tax package this year.

Alerts bearing the president’s name are stopping traders in their tracks when they pop up on their Bloomberg terminals, financiers say. Stocks briefly surged Thursday after a weeks-old clip circulated that appeared to show ex-FBI director James B. Comey affirming Trump never tried to wave him off his Russia probe (The Post had reported Comey’s notes said something different). Height Securities, which provides political research and analysis to investors, convened a call Friday morning to walk clients through impeachment scenarios.

“The investment community does not like the prospect of a president being booted out of office,” said Pete Cohn, a Height analyst. “But they see the Trump agenda going down in flames and a bit of a loose cannon in the White House, and thinking if we had [Vice President] Pence, who’s more vanilla and drama-free, it might be better for the market.”

Market players remain focused on an overhaul of the tax code as their top priority, an effort already stumbling over divisions within the GOP. Senate Majority Leader Mitch McConnell (R-Ky.) last week dismissed the chances of an import levy that House Republicans are counting on to raise roughly $1 trillion in revenue. Hopes that the Trump team could help harmonize the process took another hit Friday afternoon with the withdrawal of Jim Donovan, who had been slated to join an understaffed Treasury Department as Secretary Steven Mnuchin’s deputy.

When Trump was elected, some business interests fretted that the new president was too unpredictable and could roil a still-tepid recovery by pursuing his populist campaign pledges. But Wall Street and the markets turned immediately bullish, a bet Trump encouraged by stocking his economic brain trust with familiar faces — including Mnuchin, a former Goldman Sachs partner, and former Goldman president Gary Cohn at the National Economic Council.

Now, that confidence is sputtering.

While last week’s market spasm was touched off by the latest White House controversy, investors had already begun signaling a wariness that policymakers would deliver a big economic lift anytime soon. Booming growth drives up prices for goods and services, so inflation expectations spiked after markets decided Trump’s November victory would unleash a major expansion. But one key measure of those expectations — the so-called five-year, five-year forward inflation rate — has been falling all month. It closed last week at its lowest level since the election.

“This has been a long process, not just the last several days,” said Joshua Shapiro, chief U.S. economist at MFR.

New revelations from the Russia probe could still make stocks shudder, Shapiro said. But markets are increasingly pricing out hope of breakthroughs on taxes and the rest of the agenda. They not only reflect daily headlines suggesting that Trump’s team is busy fending off Russia-related news, but the slow progress of health-care legislation — which lawmakers and the president hoped to get out of the way before moving on to taxes. Republicans had wanted to use savings achieved in their health-care bill to pay for at least some of the rate cuts.

Congressional Republicans “have yet to prove they can walk and chew gum at the same time,” Shapiro said, “and having a president who’s damaged makes the whole process more difficult.”

There was at least one bright spot for market-watchers last week. They cheered Mueller’s appointment as special counsel, with several investors predicting it will create breathing room for Congress to return to policy — in the short term, at least.

The decision “temporarily tempered the political tsunami that emerged in recent days,” Compass Point analyst Isaac Boltansky wrote in a note to clients on Thursday.

Goldman’s Phillips said the move could help relieve Democratic demands for an independent probe. That, in turn, could take the pressure off a September showdown over a government-funding package and an extension of federal borrowing authority.

But the fact that Mueller’s intercession became necessary at all speaks to a more fundamental problem that should brace those still hoping for a fiscal boost from Washington. “The way the Comey situation has been handled is symptomatic of a lack of discipline in the White House,” Cornerstone Macro analyst Andy Laperriere said. “Passing a major tax bill is hard. If the president isn’t focused on it, it makes you wonder if he’s going to be able to deliver, and on the rest of the agenda, as well.”

Bankers themselves hold out some optimism for action that hits closer to home. Bank stocks helped lead the post-election market rally, surging on speculation that congressional Republicans would gut the regulations imposed on the industry in the wake of the financial crisis. Momentum for a legislative overhaul has faded, and the run-up in bank share prices has likewise flagged. Yet Wall Street executives still see potential for the Trump administration to act unilaterally to ease restrictions on the sector.

“It’s not totally disconnected from controversy around the White House, because the regulators still need marching orders,” one top Wall Street lobbyist said. “But there is a menu of actions they can take in their arena.”