More evidence that President Obama is building a post-convention lead over Mitt Romney.

The president now has a 5-point advantage over Romney in the Gallup daily tracking poll, 49%-44%.

Scott Rasmussen's daily tracking poll has Obama up 49%-45%, his biggest lead over Romney in that survey since March 17.

And for the second day in a row, Obama enjoys a 4-point lead over Romney in the Reuters/Ipsos tracking poll.

All of these leads have been built in the days since the Democratic convention in Charlotte.

"Obama's convention bounce is evident both in the head-to-head numbers with Romney and in his job approval ratings," Rasmussen reported.

Note that Rasmussen is a frequent commentator on Fox News, and some analysts believe his polls lean Republican (which Rasmussen disputes).

It also should be noted that tracking polls in the days ahead will take Friday's poor jobs report into account -- and that convention bounces in previous elections have eventually evaporated.

Rasmussen writes: