For one, historically speaking, the occupant of the White House has not reliably driven the market, said Koesterich, head of Asset Allocation for BlackRock's Global Allocation Fund
"In addition, if we get the most likely outcome, which is probably somewhat of a continuation of the status quo and you're still looking at divided government, it may not have as much of an impact on the market at the broad level as some have suggested."
Democratic nominee Hillary Clinton has seen an uptick in the polls since the first presidential debate. She is leading Republican nominee Donald Trump 52 percent to 38 percent in a two-way race, according to the latest NBC News/
Wall Street Journalpoll released Monday. In a four-way race, which includes Green Party candidate Jill Stein and Libertarian Party candidate Gary Johnson, Clinton leads Trump 46 percent to 35 percent.
The outcome of the election will certainly affect sectors like health care and energy, Koesterich said.
But even then there can be nuances within the sector, Koesterich pointed out. For example, pharma and biotech have come under pressure because of the controversy over drug pricing. Clinton has proposed a consumer response team to monitor price hikes. However, if Clinton wins and the Affordable Care Act continues, he said some service providers and hospitals stand to benefit.
"It's worth focusing on sectors but even within the sector expect some differentiation depending upon the nature of the business and how Washington affects their revenue and their bottom line."
A Clinton victory would also probably mean continuity at the Federal Reserve, Koesterich said. He believes the central bank is likely to hike rates in December but this is going to be a very gradual and probably a somewhat short tightening cycle.
"The terminal level you get to when the Fed stops raising rates is going to be dramatically lower than it's been in previous cycles."
Trump has been critical of the Fed and has suggested it has kept interest rates low to help President Barack Obama's administration. Chair Janet Yellen responded by saying partisan politics plays no role in the Fed's decisions.
— CNBC's John Harwood contributed to this story.