Those risks include a replacement for the Affordable Care Act, as well as a corporate tax bill on which retailers like Bentonville, Ark.-based Wal-Mart have faced off with manufacturers, with retailers worried the changes will raise the cost of imported goods. Arkansas Sen. Tom Cotton has criticized other GOP representatives over the border tax idea, saying it would "see working Americans railroaded."
CNBC contributor Larry Kudlow, who is close to Trump and his team, said on Wednesday that the White House is leaning toward the border tax.
At the same time, Wall Street is increasingly skeptical that Trump's plans to boost mostly private-sector infrastructure investment by $1 trillion over 10 years using tax credits would make it through Congress.
"I think the Trump rally is very vulnerable," said Zandi. "It's about corporate tax cuts and lots less regulation. Stock investors are attaching a high probability to both this year. It's almost a done deal in their minds. I doubt it. The odds that the Trump Administration and the Republican Congress get it sufficiently together to pass tax reform and make big regulatory changes are dropping."
The same political chaos has led to the boldest speculation of all about Trump's presidency: it won't last, either because he gets impeached or resigns before his term expires in 2021. While the president held the first rally of his re-election campaign on Feb. 18 in Florida, British betting house Ladbroke's is laying 10-11 odds his administration will end prematurely — the same odds it is offering on Trump serving a full term.
Trump's speech to Congress was judged by both sides of the political divide as his most "presidential" moment, at least in tone, providing relief to the likes of Wharton's Siegel.
But, oddly, the unlikely chance that a Trump term ends early might be even better for stocks, Zandi said. Vice President Mike Pence, who would take over if Trump left, is a fan of tax cuts and deregulation without posing the worries about trade wars that his boss does. "This is interesting. And a reasonable question," Zandi said. "Pence would be an establishment Republicans' dream come true."
It also points to a simple fact, neither all good or all bad, that both bulls and bears need to evaluate: You're dreaming if you think this rally is all about Trump.
— By Tim Mullaney, special to CNBC.com