Traders have generally leaned toward expecting a Clinton win, coupled with continued Republican control in at least the House of Representatives, which is seen helping to maintain a market-friendly state of federal government gridlock. However, both parties are generally seen as negative for pharmaceutical stocks, due to increased controversy over high drug pricing.
Last week, Bloomberg reported that the Department of Justice may file charges in its generic-drug investigation of possible collusion on drug pricing by the end of the year. Mylan and Teva were among companies named in the report as having disclosed subpoenas and cooperating with authorities.
The iShares Nasdaq Biotechnology ETF (IBB) — which is down 23 percent this year — struggled for gains on Tuesday afternoon, while the VanEck Vectors Pharmaceutical ETF (PPH) traded 1 percent lower.
Some of the biggest decliners in those ETFs came from company-specific news.
Valeant Pharmaceuticals shares plunged more than 20 percent on disappointing earnings and guidance cut.
Shares of Endo International traded more than 8 percent lower after management said the firm is facing increasing pricing and competitive pressures in its U.S. generics business and the trends will likely worsen in 2017. Teva Pharmaceutical also traded sharply lower, down more than 4 percent.
The health care sector is down about 5 percent for the year so far, making it the worst performing sector in the S&P 500 year-to-date.
—CNBC's Christine Wang and Reuters contributed to this report.