President-elect Donald Trump's victory is the sole reason the market is hitting new highs, and the rally "has a while to go," Wharton finance professor Jeremy Siegel told CNBC on Tuesday.
"When you have all the smalls stocks, large stocks, even tech stocks — which we know have had some challenges — joining with it, I don't think this is something that ends tomorrow. I think it continues through December," he said in an interview with CNBC's "Closing Bell."
Siegel had predicted a Trump win would cause uncertainty that wouldn't be good for the markets in the short run, but said in the long run the Republican's victory would be positive for stocks.
"I never thought the short run would be six hours long," he said. "I thought it would last at least a week or so."
Dow futures plummeted after Trump's win, but the markets quickly recovered and surged the day after the election, Nov. 9.
Siegel thinks Dow 20,000 is "not impossible," noting that so far Trump has been acting moderate.
"As long as he doesn't launch a trade war," everything is favorable, he said.
And while Trump has called for slashing the corporate tax rate from 35 percent to 15 percent, even a reduction to 25 percent would boost S&P 500 earnings by 10 percent, Siegel said.
"That is huge," he noted.