With stocks lower on the year, the market on Thursday entered the final three months of 2015 with the prospect of a complete turnaround that could extend the bull market into a seventh year, Citi strategist Tobias Levkovich told CNBC.
"We're talking about kind of double-digit returns — mid teens to high teens [percent] — type of returns," Citi's chief U.S. equity strategist said on "Squawk Box."
At the end of 2015, Levkovich expects 2,200 on the , which would represent a 14.6 percent rise from the 1,920 level, where the index closed Wednesday. A gain of that magnitude would completely flip the script on 2015, and return 6.9 percent.
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But the Dow Jones industrial average, the S&P, and the Nasdaq composite were in correction territory ahead of Thursday's start of the fourth quarter and after logging their worst three month stretch in four years.
"I try not to let my emotions get in my the way," Levkovich said, pointing to the August devaluation in the Chinese currency as the start of the late summer swoon, which bottomed out with a market plunge on Aug. 25.
But tracking emotions with Citi's Panic/Euphoria model, he said, "We've been five weeks in panic," which serves as a contrarian indicator. "That actually yields a 96 percent probability the markets are up a year from now."
The fourth quarter has traditionally been positive for the market, despite a historically scary October. But there's hope, because in recent years, the major stock measures have rallied in four of the past five Octobers.
But not everyone is as bullish as Levkovich.
David Bianco, chief U.S. equity strategist at Deutsche Bank, told CNBC on Thursday: "We have a few concerns for October and early November."
"Earnings season is going to be very sobering," he said. "Once again this is going to get marked down as a profit recession."
Bianco, who correctly predicted a tough summer, said: "There will be some scares in October, but I'm expecting happy holidays at the end of the year and into early next year."
He builds his case on expectations for pockets of standout earnings in "health care, parts of technology, and part of consumer" companies. "I think it's technology, health care, and big banks that lead the rally."
Bianco said he's worried about the debt ceiling fight in Washington. But he believes it will get resolved, adding "fuel to the rally."
Steven Rees, global head of equity strategy at JPMorgan Private Bank, said on "Squawk Box" that investor sentiment is very negative. "There's a lot to be worried about, whether it's China, whether it's health care, whether it's Japan."
However, he sees earnings coming in better than the really low expectations, which could help support the market next year.
"A lot of the big negatives that hurt the market this year, whether it was the energy drag, whether it was the strong dollar, become a lot less negative in the next year," Rees said.
On Wednesday, economist David Blitzer, chairman of the S&P Dow Jones index committee, told CNBC he was a "little worried" about stocks. He also said he thought it was unlikely that stocks could mount a significant year-end rally.
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Billionaire Carl Icahn really sounded the alarm on stocks this week with the release of a self-produced video called "Danger Ahead."
The activist investor expressed concerns about stocks, saying the market could go down "a lot more" as investors come to grips with bubbles exacerbated by the Federal Reserve's near-zero percent interest rate policy.
One of the biggest questions marks for stocks is when the Fed might increase interest rates. Last week, Fed Chair Janet Yellen reiterated the hope for a move this year, after central bankers decided not to hike rates at their September meeting.
"The Fed kind of messed up that call," Levkovich said. "The market was certainly poised for rising rates [last month]. I don't understand how the market monitoring group at the Fed just didn't see that. It was too plain and obvious."
The Fed meets again this month and then in December, which is seen as the more likely of the two gatherings for a move.
The government's September employment report, due out Friday morning, will be watched closely by investors for clues on what the Fed might do. Strong data could bolster the case for a hike.
But Levkovich warned not to look at any one report as the trigger. "I don't think there's a single magic bullet there that's going to say ... we've turned the corner."