The World Bank expects the U.S. economy to grow at 2.2 percent in 2018, while many firms, like Goldman Sachs, expect equities to continue climbing, but that could change if there's a blowup in Washington.
With Donald Trump's erratic and often offensive behavior, an ongoing special counsel investigation and an increasingly divided American public, domestic issues could get in the way of a continued bull market.
Nothing has derailed equities so far, with stock markets hitting 26,000 on Tuesday and stocks hitting all-time valuation highs — the S&P 500's price-to-earnings ratio is around 24 times.
However, if significant information from, say, the Mueller investigation comes out or Trump sends a particularity egregious Tweet, then stocks could turn quickly, says Tony Natale, vice president and manager of strategic research at Bryn Mawr Trust, Pennsylvania-based financial firm.
"The amount of complacency we saw in 2017 was pretty amazing," he says. "So if there's some perception that one of the risks comes to fruition, given how truncated the volatility has been, we could see a giant sell-off."
If the U.S. market does react to a domestic issue, then that could spread to global stocks. "There's an old saying, when the U.S. sneezes, the rest of the world catches a cold," he says. "If something unexpected happens to us, then we could see a downturn elsewhere."
— By Bryan Borzykowski, special to CNBC.com