The thing to look at is where Romney is stuck at in most of these polls, which is 44-46% and some times lower and that doesn't seem to really changing.
That's something an incumbent worries about. What these polls show is that Romney has a lot of room to grow. People who don't want to vote for the president will either vote for the challenger or stay home, they won't change their mind and just vote for President Obama. That's why an incumbent who can't get over 50% in polling signals big trouble for that campaign. If Romney is at 44 percent in October, then he'll worry. But 44% in May/June--and ties in key swing states--is hardly a bad sign.