Political uncertainty may add to pressure on the sharemarket after Julia Gillard accepted a request from Labor Party powerbroker Simon Crean for a party vote on who should lead the party to the federal election in September.

The S&P/ASX200 is down 0.1 per cent at 4960.5 after hitting an intraday low of 4947.8 after Mr Crean's statement.

The vote will take place at 4.30pm AEDT.

"It's a bigger worry for the overseas investors because they've been baffled by Australian politics in the past few years," BBY institutional trader Anson Rosewall said.

"The real test would be if share trading volume were to increase in this downtrend as major funds start liquidating some of their exposure."

He says the index is finding support from the 50-day moving average at 4956, but a break of yesterday's low at 4937 could trigger a fall to the January 31 low at 4866.

"The market wants to pullback and consolidate, and in the mean time it will probably dismiss any positive fundamental news," Mr Rosewall said.