A Trump win would sink stocks. What about Clinton?

Investors favor a Clinton presidency
Investors favor a Clinton presidency

If Donald Trump wins the election, U.S. stocks (and likely many other markets overseas) will almost certainly tank.

How big of a drop? Forecasting firm Macroeconomic Advisors predicts an 8% fall in the U.S. A new paper out Friday from the Brookings Institute projects a 10% to 15% nosedive. You get the idea.

A Trump victory would be "America's Brexit." It would shock U.S. and global markets, much like the surprise June referendum in the U.K. where 52% voted to leave the European Union.

Almost everyone on Wall Street currently predicts Hillary Clinton will win the White House. A Trump triumph would likely cause investors to flee stocks to the safety of gold and bonds. Trump is the king of unpredictability (something Wall Street hates), and he's campaigned on an anti-trade agenda, which wouldn't be good for big business.

But what about if Clinton wins?

Don't expect a big rally, warns Peter Boockvar, chief market analyst at The Lindsey Group. In fact, markets might take a dip then too.

Related: Investors really want Clinton to win now

First of all, the market is already pricing in a Clinton win. The gains have already happened. U.S. stocks rallied after the first and second debates as Clinton gained momentum. (In addition to stocks, other market metrics like the Mexican peso also rallied as Trump's chances dimmed).

But after the third debate -- one which many believe Clinton won decisively -- stocks barely budged.

"The election is just a sideshow," says Boockvar. "The main driver of the markets is not the election. It's central banks and ultra low interest rates."

That said, investors, like everyone else in the world, will be watching what happens on Election Day. As the results roll in that evening (and possibly into the next morning), investors could still get unnerved, even if Clinton wins.

Related: Stocks would fall 8% if Trump wins, forecasting firm says

Watch out for these scenarios:

1. Do the Democrats win back the Senate? What about the House of Representatives?

The reason Wall Street really wants Clinton to win is because a) she's a known quantity and b) investors believe it's important for a Republican-controlled Senate and House to keep a Democratic President in check. "Markets love gridlock" is a common saying on Wall Street.

But as Clinton surges in the polls, there's a growing fear that the Senate -- and even the House -- could flip if voters come out strongly for the Democrats.

There's a 71% chance that Democrats regain control of the Senate, according to polling site FiveThirtyEight. That would make it easier for more liberal (and anti-Wall Street) senators like Elizabeth Warren to wield greater influence on taxes, regulation and spending priorities.

But what would really scare Wall Street is if the House also tips to the Democrats. That's far less likely -- only about a 6% chance, according to the political prediction market on CNN.

Related: Trump? Clinton? Who cares? Market focused on Senate

2. A repeat of the 2008 Obama market drop. The other red flag for investors is what happened in 2008. Barack Obama was widely expected to defeat Republican John McCain. His victory was "priced in," yet the S&P 500 rallied 4% on Election Day and then fell 5.3% the day after.

What happened in 2008 isn't that unusual.

Bespoke Investment Group looked at how the U.S. stock market performed every Election Day and post-election day since 1984. What they found was this: "The day of the election has historically been positive for stocks, the day after has been notoriously weak."

The average sell-off is about 1%, Bespoke found.

All the "market metrics" CNNMoney has been tracking in October now point to a Clinton victory -- except one. But be weary of reading a Clinton win as a boost to stocks, at least in the short term.

--CNNMoney's Patrick Gillespie contributed to this report.

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