* Clinton has 90 pct chance of defeating Trump -poll
* "Trump ETF" at session high; VIX trade lowers
* Investors point to early voter data from VoteCastr
* Indexes climb: Dow 0.45 pct, S&P 0.37 pct, Nasdaq 0.47 pct (Adds details on stock moves, comment)
By Noel Randewich
Nov 8 (Reuters) - U.S. stocks rose for a second straight session on Tuesday, helped by early voter turnout estimates favoring Democrat candidate Hillary Clinton in the U.S. presidential election.
Wall Street sees the former secretary of state as lending greater clarity and stability to the markets, while Republican candidate Donald Trump's stance on foreign policy, trade and immigration is less certain.
Data company VoteCastr, which is providing real-time election information through news outlets, including Slate, showed Clinton with an early lead among voters in Florida, a must-win state for Trump.
Several investors said VoteCastr's data had pushed stock prices higher, although they were cautious about its accuracy.
"We were dramatically oversold. People were nervous Trump would win," said Michael James, managing director of equity trading at Wedbush Securities in Los Angeles. "There's likely to be additional volatility in both directions between now and the end of the day."
Shortly after 2 pm ET, the Dow Jones industrial average was up 81.43 points, or 0.45 percent, to 18,341.03, the S&P 500 had gained 7.89 points, or 0.37 percent, to 2,139.41 and the Nasdaq Composite had added 24.52 points, or 0.47 percent, to 5,190.69.
Stocks opened slightly lower, then turned positive and extended morning gains.
Clinton has a 90 percent chance of defeating Trump, according to the final Reuters/Ipsos States of the Nation poll released on Monday.
She was on track to win 303 votes in the electoral college to Trump's 235, clearing the 270 needed for victory. She also leads Trump by about 44 percent to 39 percent in the popular vote, according to the poll.
The S&P 500 has surged 2.7 percent since the FBI said on Sunday it would not press criminal charges against Clinton over her use of a private email server, an announcement seen as improving her chances at the polls.
Shares of Smith & Wesson Holding and Sturm Ruger & Co both rose over 1.5 percent. Their sales have benefited in the past from fears among gun owners of increased gun control.
Aetna and Anthem jumped more than 2 percent. Both health insurers have gained from the Affordable Care Act, which Clinton has vowed to extend.
Advancing issues outnumbered declining ones on the NYSE by a 1.70-to-1 ratio; on Nasdaq, a 1.62-to-1 ratio favored advancers.
The S&P 500 posted 20 new 52-week highs and 3 new lows; the Nasdaq Composite recorded 54 new highs and 66 new lows.
Additional reporting by Yashaswini Swamynathan and Tanya Agrawal in Bengaluru, Dion Rabouin, Sinead Carew and Lewis Krauskopf in New York; Editing by Dan Grebler