Gallup Poll: Obama Convention boost now gone

(CNN) -- After a wave of post-convention approval, President Barack Obama's lead has faded, according to the latest Gallup daily tracking poll Tuesday, September 18th.

Gallup's seven-day rolling average indicates that 47% of registered voters supporting Obama and 46% supporting Mitt Romney, returning the race back to narrow, pre-convention margins.

The president's lead was as high as seven points in Gallup's daily tracking poll last Wednesday.

A CNN Poll of Polls which averages the seven national survey of likely voters conducted following the conclusion of the Democratic National Convention earlier this month indicated that 49% of likely voters were backing the president, with 46% supporting the Republican nominee.

While the Gallup poll samples registered voters, it will move to sample the smaller pool of likely voters in the next few weeks as November draws near.

This latest edition of the Gallup poll was conducted September 11-17, nearly entirely before Monday's release of secretly recorded clips of Romney speaking at a private fundraiser in May that critics charge portray him as out of touch with ordinary Americans. Those clips have dominated coverage of the campaign trail over the past 24 hours.

The Gallup daily tracking poll is based on telephone interviews with approximately 3,050 registered voters; Margin of error is plus or minus two percentage points.

CNN's Dana Davidsen and Paul Steinhauser contributed to this report.