Here’s how to tell Michael O’Rourke is working: he’s awake. He’s more or less always staring at stock screens, in case a headline passes or one of Donald Trump’s 280-character zingers blows up the market.

“I’m logged on probably 16 to 18 hours a day. You just don’t know when his tweets are coming,” said O’Rourke, JonesTrading’s chief market strategist. Prepare all you want by looking at companies or the economy, but it hardly helps. “You can’t analyze how a politician or a policy maker is feeling.”

With three days left until the midterms, traders are struggling to assess the impact on markets. But there is one thing they’re pretty sure of: if the president’s enemies prevail, bouts of Twitter-induced panic on trading desks will only get worse.

“It’s something we’ve had that’s been a feature of markets: the tweet risk,” said Matt Forester, chief investment officer who oversees about $8 billion at Lockwood Advisors. “We’ve been polarized, and I don’t see that changing.”

Around the world, traders have gotten used to the pattern. Trump tweets, and the markets move. It happened Thursday, when he said trade talks between the U.S. and China are “ moving along nicely’’ and stocks soared. In April, he criticized big tech companies and they plunged. Oil prices and the dollar have also felt the wrath.

So whether he’s vacationing in Italy or going to the bathroom, Donald Selkin of Newbridge Securities keeps an iPhone or iPad on him — in case he needs to trade.

“The news cycle moves very, very rapidly,’’ said Selkin. “There’s been comments from the president and top administration officials — some of his tougher rhetoric about trade and imposing tariffs — and the market came down.’’

Shocks could multiply if Democrats win. Polls, fundraising and the sheer number of competitive House districts give Democrats good odds of winning control of the chamber. But it’s a tougher path for them to a Senate majority, and the consensus of independent analysts is that Republicans will hold on to their majority there. While market watchers love to say gridlock is good, that might not necessarily extend to people’s nerves.

“If Democrats get control, I think you’re just going to have a lot more volatility,’’ Avenue Capital co-founder and chief executive officer Marc Lasry said. “And the reason you’ll have a lot more volatility is you’re going to have more headlines, you’re going to see more of all these problems that you’re having in D.C. with the president and Congress.’’

Coming up with a trading thesis from past political alignments is tricky. An OppenheimerFunds report looking at the Dow Jones Industrial Average starting from 1901 shows the market usually outperforms under a divided government. Then again, Ned Davis Research found the combination of a Republican president and a split Congress has resulted in the Dow falling an average of 6 percent a year.

For the most part, strategists and investors believe the polls, even after Brexit and the 2016 presidential election.

“The view is that the polling is right and that Democrats will narrowly take the House and Republicans will keep the Senate,’’ said Jonathan Golub, the chief U.S. equity strategists at Credit Suisse. “From a practical view, it won’t change a whole lot. You could say it’s already baked in.’’

Which brings us back to the tweetstorms.

“Even if we have gridlock, there’s still the concern of can the Democrats bring up more congressional support to dive deeper into some of the allegations that are out there,’’ said Jeff Carbone, managing partner at Cornerstone Wealth. “That would bring up more fear and concern.”

It doesn’t help that the S&P 500 just had its worst month since 2011, falling 7 percent in October. Explanations included coming rate hikes from the Federal Reserve, trade anxiety, and signs economic and earnings growth have peaked. Trump said it was a little pause due to anxiety around midterms. “If you want your Stocks to go down, I strongly suggest voting Democrat,” he tweeted.

Not everyone sees brewing disaster. Unless Democrats win the Senate, it’s unlikely things will get to a point that lawmakers vehemently consider impeachment, according to Leon Cornelissen, the chief economist for Netherlands-based Robeco. That probably won’t happen, he says.

John Toohey, head of equities at USAA Asset Management Company, said the back-and-forth will be just that — and not much more.

“There’s always noise in Washington and if business leaders can operate, then it’s just noise,’’ said Toohey. “Just more and more investigations, I don’t want to say that’s business as usual, but certainly when it comes to Washington, it feels that way.”

Noise, maybe, but it doesn’t mean anyone is actually looking forward to more of it.

“Your Republican clients are excited about it and your Democrat clients think the world is ending,” says Brian Frank, president at Frank Capital Partners. “It was all social media hype, especially by the President on Twitter himself, and it turned out to be a puff of smoke.’’

Regardless, “I’ve definitely worked a lot more sleepless hours.”