world news tonight evening newscast has officially overtaken underfire rival nbc 's nightly news in the ratings war .
nbc 's 288 consecutive week winning run had stetched back to september 2009 and the drop comes two months after brian williams ' suspension .
an nbc spokesperson said the network was ` pleased ' with substitute anchor lester holt 's ` strong performance '
switch also follows a change in how the numbers are crunched and nbc is now prevented from including repeat numbers from overnight replays .