Now we know what it takes for Wall Street to wake up to Trump risk

For months, traders have been wondering what it would take to shake confidence in a record-breaking market that has seemed immune to presidential scandal.

After all, investors piled into the markets after Donald Trump's election victory - betting on anything and everything that could profit from tax cuts, the gutting of regulatory agencies and infrastructure spending that he promised.

And for months, those same investors looked past distractions like a failed healthcare vote and the Trump administration's lack of preparedness on key issues. The infrastructure spending, we learned, might not happen until 2018 if at all. The tax "plan" isn't even that - it's a hastily pulled together a one-page list of goals that looks more like a campaign pledge.

Apparently, talk of a potential impeachment of Trump - after his reported strong-arming and then firing of FBI Director James Comey - has gotten investors' attention. To be clear, it's not that investors are necessarily taking an impeachment as likely. It's that the challenge to Trump's political power has reached a level that means his economic agenda is off the rails.

The dollar is sliding against major currencies and stock markets are sagging around the world. US stocks followed that lead, suffering their worst decline in 2015, with the Dow Jones Industrial Average tumbling nearly 250 points. In the bond market, a flattening of the Treasury yield curve, which occurs when the gap between long- and short-term interest rate narrows, also portends expectations of weaker economic growth ahead.

"Claims that President Trump tried to strong-arm ex-FBI director Comey into dropping an investigation merely add fuel to the existing fires of political uncertainty, apparent White House incoherence slowly sapping faith in stimulus policies getting even partisan approval," wrote Mike van Dulken, head of research at Accendo Markets, in a note to clients.

Even Trump's staunchest economic defenders appeared to be waving a white flag.

"The stock market is really jittery right now," admitted Stephen Moore, a former Trump campaign advisor, on CNN. "They want him to focus on what he got elected to do, to reform the tax code, healthcare" and boosting economic growth. Instead, the scandals may be hurting the economy by raising uncertainty, Moore said.

Of course, the Comey scandal has taken on a life of its own.

It's impossible to determine whether today's moves are the beginning of a longer-term market slump or just a blip on the radar. Still, given how many shoes still appear ready to drop in the Trump-Russia investigation, it's at the very least likely these blips will become increasingly frequent - and investors aren't taking anything for granted anymore.