"The worst-case scenario is it continues to be a draw on the Democratic side, and nobody else is gaining momentum on the Republican side," said Art Hogan, chief market strategist at Wunderlich Securities.
Analysts say Wall Street expectations are high that Trump will sweep the Republican contests in 11 states, but if any of his more-traditional GOP rivals makes a stronger-than-expected showing Tuesday, the market could get a lift. On the other hand, if front-runner Clinton looks weaker than expected against Vermont Sen. Bernie Sanders, a self-proclaimed democratic socialist, that could be a negative for stocks.
The week following Super Tuesday has historically been a positive time for the stock market. In the six Super Tuesdays going back to 1992, the market has been higher one week later every time, with a median gain of 0.88 percent, according to analytics firm Kensho. Materials, consumer discretionary and industrial stocks also gained each time, while the biggest underperformer during the following week was health care, but it was also positive.
"If Trump wins and wins big I don't expect a big market move because it's priced in," said Brian Gardner, director of Washington research at Keefe, Bruyette & Woods. "If he underperforms and another candidate shows viability, I think the markets would be happy to see a traditional candidate doing well."
Gardner said Clinton has regained control of the race. "Every poll I see has her up big in Super Tuesday states. She has the super delegates. It seems to me the party is coalescing around her. She may not put it away Tuesday, but it's virtually impossible to see a path forward for Sanders," he said.
The market is more comfortable with Clinton than Trump, and she is widely expected to win the election. "There are certain sectors that will lose but there is familiarity with Clinton, and the market will be OK with that," said Gardner.
But Trump is viewed as too unpredictable, and he could keep the level of uncertainty high. "Donald Trump is trying to make America great again but instead of inspiring people, he's playing to their worst fears," said Gardner. "There are some conservative Republicans that label Trump a 'fascist' and they would never vote for him." He said Trump stumbled this past weekend when he did not immediately disavow the former leader of the Ku Klux Klan.
Analysts say, however, that the Republican Party would be helped if it looks like the economy is heading into a recession in November. Gardner also said Republicans have typically won in years when voter turnout is light.
"The wild card of course is turnout. Both (Trump and Clinton) candidates have very high net negative numbers and we could see a very low turnout. Who knows who benefits from that," Gardner said.
Trump is seen as leading in most Super Tuesday states but Sen. Ted Cruz could win his home state of Texas, Gardner said. He also said Sen. Marco Rubio of Florida is a candidate that has tended to pick up voters among those who make their decision at the last minute. Ohio Gov. John Kasich is not expected to win any Super Tuesday states.
"At this point Cruz, Rubio, Kasich are trying to see how many delegates they can amass and if they can keep Trump close, and keep from getting a majority of delegates before they meet in Cleveland. It's tough to see a path forward for anybody other than Trump to get a majority of delegates," said Gardner.
Jerry Webman, chief economist at OppenheimerFunds, said the markets are basically pricing in victories by Trump and Clinton, but Tuesday's races may help in focusing the markets on issues. "We get closer to nominees after (Tuesday). We might know pretty much who both nominees are going to be. Maybe, maybe not," he said. "Then I think people should start paying attention to nominee platforms. How that helps and how it doesn't help."
Webman said Trump has clear ideas on some tax law, and would like to get rid of carried interest. He also may propose tariffs or attract retaliatory reactions around trade because of his protectionist views.
"Trump is probably more aggressive on national defense. Clinton is more hawkish than Obama. That would be positive for aerospace and defense. Both would be positive for defense but probably more so Trump than Clinton," said Webman. He said if Clinton were to become aggressive on Wall Street, that would be positive for regional banks.
"Health care ... is one where investors should pay close attention, particularly on pharmaceuticals and expensive medical equipment," said Webman.
As for the financial sector, Gardner said it's hard to tell where exactly Trump stands. "It's really impossible to say what a Trump presidency means. He's blasted Dodd-Frank. That's typical of all the Republicans, but he doesn't say what he would do. Until we see who is advising him on the financial sector policy, who might be in the administration, who he might appoint to the regulatory agencies, we don't know. I think that's a negative for financials. The lack of uncertainty is eventually going to start to disturb some investors in the sector," he said.
Clinton is not seen as positive either but she has given more clues on the direction she would take. "She's pretty clear that she's not looking to break up the universal banks. She's looking more at the nonbank financials and the shadow banking system. I think the hedge fund world and asset managers would maybe slightly underperform, but I think investors expect her to take a cautious approach. I think they understand the campaign rhetoric," he said.
But Webman said the election brings a bigger concern, and investors should protect themselves by diversifying globally. "Not that the election is a negative for the U.S. but there is going to be uncertainty about the regulatory environment for U.S. companies," he said.
Gardner said he is watching congressional primary races in Alabama, where Sen. Richard Shelby, chairman of the Senate Banking Committee is seeking re-election, and Texas where House Ways and Means Chairman Kevin Brady is running against four opponents.
"He's got to get a majority to avoid a runoff. So is the anti-establishment fervor going to cause Brady problems? Brady is a rock-solid Republican. If he has problems, the alarm bells are going off," he said.
Disclosure: NBC Universal, CNBC's parent, is a minority investor in Kensho
Update: Clarifies that Republican contests are in 11 states.