Ryan isn’t at the top of the ticket.
Neither party has a popular candidate so you'll see this all the way to election day.
So, how do you keep ahead of this? Well, you can keep your eye on Joltin' Joe Biden ~ every time he's turned loose to embarrass somebody, or intimidate them, the Democrats lose share ~ not a lot ~ but maybe 100,000 votes. These are permanant losses too, and they do show up in the popularity ratings.
With Republicans, getting Ryan on board with a show merely reminded yet more of them of how little they like Romney. Bing Bong there goes the bounce.
Once the conventions are over we'll see the pollsters turn entirely to PROBABLE VOTERS. First, there's an initial statistical problem ~ there are a lot of people NOT PLANNING ON VOTING for president this time. Once the pollsters get a grasp on that, they'll adjust the numbers and you might even see a jump up in both major candidates, but that'll be swiftly whittled down ~ and finally, the race will be decided by only the true believers who, if you can believe it, actually think highly of Obama or Romney. These people are immune to the issues!
I expect an historically low turnout for President this time with both candidates getting fewer votes than were voted for their party counterpart last time, and actually maybe no more votes than are cast down ballot.
Usually the votes for President are greater than those for Representatives ~ this time I"m suggesting they'l be less ~ without looking I"d guess the last time that happened was back in the 1820s or something.