(Adds portfolio manager comment, updates prices to close)
* TSX ends down 78.47 points, or 0.53 percent, at 14,619.46
* Nine of the TSX's 10 main groups fall
By Alastair Sharp
TORONTO, Sept 26 (Reuters) - Canada's benchmark stock index fell in a broad retreat on Monday, tracking U.S. indexes lower as investors took a cautious turn ahead of the first U.S. presidential debate and as energy shares failed to move higher with a bounce in crude oil prices.
The Toronto Stock Exchange's S&P/TSX composite index closed down 78.47 points, or 0.53 percent, at 14,619.46.
The three main Wall Street indexes all shed at least 0.85 percent, as investors focused on how Republican presidential hopeful Donald Trump would fare in a televised debate against Democrat Hillary Clinton, which could rank as one of the most-watched and highly-anticipated political showdowns in U.S. history.
"People are getting just a little bit more defensive ahead of the debate tonight, and may be raising a little bit of cash in anticipation of some volatility if the earnings season is weak," said Manash Goswami, a portfolio manager at First Asset Investment Management.
Valuations have pushed ahead of fundamentals, he added, raising the risk that the TSX may fall further from here.
"Either earnings and economic data needs to start to really tick up or the market needs to pull back. It's one or the other," Goswami said.
In Canada, heavyweight financial stocks led the losses, while consumer names also fell.
Valeant Pharmaceuticals International Inc lost 6.3 percent to C$34.25. The company has previously been criticized by Clinton over its drug pricing strategy.
Oil settled up 3 percent as the world's largest producers gathered in Algeria to discuss ways to support prices, after a similar meeting in April to freeze output failed.
But the jump was not reflected in Canada's large energy sector, which ended barely lower.
The most influential weights included Royal Bank of Canada , which fell 0.6 percent to C$80.89, and Toronto-Dominion Bank, down 0.6 percent to C$57.82. The financials group slipped 0.6 percent overall.
TransCanada Corp fell 1 percent to C$62.34. One of its units, Columbia Pipeline Group, offered to buy Columbia Pipeline Partners LP for about $848 million in cash.
The materials group, which includes precious and base metals miners and fertilizer companies, fell 0.5 percent.
Of the index's 10 main sectors, only telecoms gained, adding 0.2 percent. ($1 = 1.3161 Canadian dollars) (Reporting by Alastair Sharp, editing by G Crosse)