New York Times Saberpolling guru Nate Silver says “it’s a bad sign for Mr. Romney that Mr. Ryan has produced a below-average bounce so far.” The Romney-Ryan boosters aren’t having it; they’re feeling confident — cocky, even.

Sadly, I can’t do numbers like Silver. What I can do is deja vu:

“Palin bounce has Democrats off balance” — Los Angeles Times, Sept. 10, 2008

“With Palin at His Side, McCain Finds Energized Crowds” — New York Times, Sept. 10, 2008. (The lede: “What a difference a running mate makes.”)

“McCain-Palin Campaign ‘Chemistry’ Energizes Republican Crowds” — Bloomberg, Sept. 9, 2008

“Panic Time for Obama …” — Scared Monkeys, Sept. 7, 2008

“As the remarkable two-week stretch of back-to-back presidential nomination conventions ends, a weekend USA Today/Gallup Poll finds that the John McCain-Sarah Palin ticket has more than matched the Barack Obama-Joe Biden ticket’s convention bounce of last week with a ‘rebound’ bounce, and in the immediate aftermath of the GOP convention McCain and Palin now have a slight edge over their opponents.” — Gallup, Sept. 8, 2008.

“Sarah ‘Barracuda’ Palin has given McCain the sort of bounce Biden couldn’t. Obama went from a 48/40 lead before the RNC convention to no lead at all. … It’s amazing what an actual conservative can do for a Presidential ticket.” — SayAnythingBlog.com, Sept. 5, 2008.

“Still bouncing: New Gallup gives McCain five-point lead over Obama” — Hot Air, Sept. 8, 2008

You get the idea. Romney-ites will insist that Paul Ryan won’t land on his face like Palin did. I agree. They’ll point out, furthermore, that there won’t be a dramatic Lehman Bros./AIG meltdown this year — or that if there is one, it would redound to the benefit of the opposition party. Also true. But Ryan’s liabilities are real — and I suspect the GOP’s own version of “Mediscare” this week will only temporarily obscure that fact.