For all the political turmoil, for all the breathlessness of the recent chaos in Washington, markets have been largely indifferent. Or at least they were: this week, there are signs things may be shifting.

On Wednesday, as the political bedlam reached a boil in D.C., spooked investors helped drive several U.S. indexes down to the lowest levels seen in eight months.

"It's certainly a day when the chickens are coming home to roost," Donald Selkin, chief market strategist at Newbridge Securities, told Reuters.

On Wednesday, the U.S. dollar fell dramatically, giving up the gains it made since Donald Trump took office. Bank stocks were clobbered. And tech stocks fell 2.8 per cent. Then there's the VIX. Technically it's a measure of the implied volatility in markets. Colloquially, it's known as Wall Street's fear index.

It soared 46 per cent on Wednesday.

"It is important not to read too much into a single day of trading," David Rosenberg, chief economist at Gluskin Sheff and Associates, wrote in a note to clients. "But the cracks are really starting to add up here for this once-Teflon market."

How did we get here?

To figure out where things go now, it's best to start with how we got here.

Remember — very few expected Trump would win. Many experts predicted markets would tumble, the U.S. dollar would fall and the economy would be hurt if he somehow carried the day. But markets soared as investors embraced Trump's plan to cut taxes and regulations.

When Trump fired former FBI director James Comey, investors shrugged. The markets didn't blink when Trump was accused of leaking classified information to Russia.

By mid-week, though, cracks began appearing.

"The mood has shifted tremendously here in Washington D.C.," says Edward Harrison, founder of Credit Writedowns.

Why the sudden change

So, what happened? Why did this crisis prompt a sell-off? Fundamentally, investors appear concerned that Trump's market-friendly policies are in peril. That whatever political capital Trump needed to get his agenda through may now be eaten up dealing with scandal.

Trump's administration has been beset by leaks and political turmoil in recent weeks, as investigations continue into possible links between his campaign and Russia. (Kevin Lamarque/Reuters)

Much of the bull run was built on solid economic fundamentals and first-quarter earnings. But there's no question the promise of Trumponomics was filling the sails as stock markets soared. And if that agenda is in trouble, so too is the bull run.

"All the oxygen is getting sucked out of the room by all this scandal in Washington," says Harrison.

Rosenberg has a similar view, telling his clients there is an elevated risk that whatever was going to be done on deregulation, tax reform and infrastructure "will be delayed if not derailed as Washington's focus is diverted to this unfolding crisis."

This could go on ...

Back in New York, Selkin from Newbridge Securities says the real question isn't about one day or even a couple of days. His concern is the long-term.

"The (equity) bull market is not over by any means, but between the political stuff and the fact that the next earnings season is three months away, there's going to be a lack of motivation."

Investors have seen some pretty solid returns since Trump took office. But if they decide now is the time to cash out, the question becomes how deep and how long a sell-off might be. The answer is anyone's guess.

But at the very least, it seems the political circus that has roiled Washington is heading north to Wall Street.