At this point, it's no contest.
While I'm not sure what was the significance of February 5th, I suspect it was around then that the wheels started to fall off of the McCain candidacy.
Adding to Rudy's growing momentum is the tact that Mitt Romney's "I'm pretending to be a staunch conservative" roadshow has yet to gain traction.
For a nonRudy campaign data source, look at these charts on RealClearPolitics.com. Note on the graph how McCain's slippage mirrors Rudy's gains.
Expect social conservatives and leftists to gin up "swift-boat" type attacks on Rudy--his politics and his personal life. (And just today, the NYPost went after Judy Nathan Giuliani ran with a story about her first marriage.)
While one would think that the anti-Rudy campaigns would benefit his likely Democrat opponent, it'll probably be a wash at the end. Why? Because that candidate--whose likely to be Clinton--will undoubtedly face his/her own "swift-boating".