US markets were softer, geopolitical tensions continued, and the oil price was firmer. (Image: NZME)The New Zealand sharemarket fell slightly amid uncertainty over the National Party leadership and the continued impasse in the Middle East negotiations, while the oil price rose.The S&P/NZX 50 Index weakened in the afternoon when it was known the National Party was holding an urgent caucus meeting (Wednesday morning) and closed at 13,860.66, down 27.58 points or 0.2%.There were 71 gainers and 65 decliners on the main board, with 34.3 million shares worth $124.4m changing hands. 'Heavyweights'Jeremy Sullivan, investment adviser w...