The Dow Jones Industrial Average crossed the 30,000 threshold for the first time ever Tuesday, capping an astounding run from the depths of the pandemic last spring when the index bottomed out just above 18,000.

Investors were feeling optimistic on three fronts. First, vaccine optimism was flowing Monday with the announcement that a third candidate from AstraZeneca was up to 90% effective. Second, news late Monday that the Government Services Administration, which had been stalling the transition from the outgoing Trump Administration to the incoming Biden Administration, would begin its formal handover process, came as a relief to those who had feared an extended transition-of-power crisis.

And finally, yesterday's news that Biden was poised to name Janet Yellen Treasury secretary was also greeted warmly by Wall Street. Not only is she a steady hand—someone the Washington Post called "a battle-tested leader who helped the nation recover from the Great Recession"—she is seen as a supporter of government stimulus. Moreover some on Wall Street had feared a more progressive choice would have roiled the stock market and favored heavier regulation.

Ryan Detrick, Chief Market Strategist for LPL Financial wrote in a note Monday that "The reaction from stocks since the US election has been truly impressive. The S&P 500 Index is up 8.8% for the month, on pace to be the best November for the S&P 500 in 40 years. Small caps have also soared, with the Russell 2000 Index up 16%, which would be its second-best month ever. Although we remain longer-term bullish on equities, there are some signs that sentiment could be getting a little frothy at the moment, which could increase the odds of a pullback."

The runup in small cap stocks has been sizzling, with the Russell 2000 on track for its best month ever. That in particular is a sign, say some analysts, that the underlying economic conditions are on the mend, given the index increased sensitivity to changes in GDP and the economic cycle.

Still, spiking COVID cases and the upcoming Thanksgiving holiday are a worrisome backdrop to the exuberance in the stock market. In fact, economists at Goldman Sachs recently lowered their GDP estimates for that reason. "The bank cited 'the rapid and broad-based resurgence of the coronavirus' as the main reason it was downgrading Q4 and Q1 GDP forecasts. Goldman now expects +3.5% and +1.0% annualized growth in Q4 and Q1 (+4.5% and +3.5% previously)."

That's one reason some bearish investors aren't convinced we'll stay at these levels. James McDonald, CEO of Hercules Investments in Los Angeles wrote in a note Tuesday that, his firm is preparing for a 20% stock market pullback between now and the inauguration, and that he sees substantial risk in rising COVID-19 cases, continued election uncertainty and the likelihood of insufficient fiscal stimulus from Congress.

"While Dow 30,000 is a symbolic moment for the stock market, it is simply a continuation of the market's euphoria after the pre-election selloff. At the end of the day, Dow 30,000 is just a number and the milestone doesn't hold any credence in determining the near-term stock market outlook," McDonald writes.