The stock market stuttered on Wednesday after President Donald Trump's abrupt firing of FBI Director James Comey added to investor unease around the ability of the administration to focus on the pro-growth agenda Trump promised from the campaign trail.

The Dow fell by as much as 70 points in mid-morning trading, and the dollar edged lower against a basket of foreign currencies.

Wall Street has enjoyed a record-breaking streak since Trump's November victory, largely attributable to investor confidence in the President’s promises on deregulation, tax breaks, and infrastructure spending.

However, the new controversy unfolding in Washington is making investors nervous that the increasing number of distractions will prevent — or, at best, delay — the introduction of the reform policies upon which they've been banking.

"I think it's still another story that's going to slow down Trump's agenda," Greg Valliere, Horizon Investments chief global strategist, told CNBC. "We're going to have a budget fight in the next few months. Nobody has any idea what the Senate is going to do on health care. You have another huge story that's going to gobble up more time. It's a distraction for sure."

President Trump shocked political pundits on Tuesday night after he fired Comey, citing the way the FBI chief had handled the Hillary Clinton email server scandal last year.

The move has created controversy on the Hill and beyond, since Comey was at the helm of a probe into Trump’s alleged ties to Russia at the time he was dismissed. Senator Bob Casey described Comey's removal as “Nixonian,” and Senator Elizabeth Warren said Comey was fired “because of the Russians.”