In a surprising swing since Mitt Romney announced Wisconsin Rep. Paul Ryan as his running mate last weekend, the Republican candidate has ceded 5 points to President Barack Obama in the Rasmussen daily tracking poll.

Last Friday, Romney led Obama 47 percent to 43 percent in the tracking poll, which compiles results based on a three-day rolling average of 500 likely voters. This Friday, he's trailing Obama, 46 to 45 percent.

It's the first lead that Obama has taken in the Rasmussen daily tracking poll in the last 10 days, in fact.

Ryan's effects on polls have been mixed so far, but early returns show that he's having a more positive effect in swing states than national polling. Despite a brief bump in the Gallup tracking poll, Ryan hasn't propelled the ticket the same way Sarah Palin did for John McCain in 2008. But Romney's position has improved in crucial Virginia, Ohio and Wisconsin polls.

Still, the Rasmussen poll should be concerning for the Romney campaign. So should Obama's approval rating, which has also jumped 5 points in the past week.