Showbiz
Rex Features
The pair were spotted together at Tuesday's Purple Ball, held to celebrate Barack Obama's inauguration, leading to speculation that they are a couple.
"They were so lovey-dovey," a source said. "They were nibbling on each other's necks, gazing into each other's eyes and doing a lot of flirty touching."
McAdams, star of The Notebook and the upcoming Sherlock Holmes, split from Ryan Gosling last year but later attempted to rekindle their romance.
Lucas has reportedly dated Salma Hayek, Heather Graham and Anne Hathaway.
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