There's another theory of the case that Chandra was abducted from her bed the night before and the computer searches and dumping of the body in the park were staged to make it appear like a random violent crime. Neighbors of Chandra reported hearing a bloodcurdling scream in the middle of the night the night before she disappeared.
It's possible, I suppose, that Chandra was abducted at some point before she is thought to have left for a run in the park but it seems highly unlikely.
Her computer had been used that morning, she'd read email and done some web surfing. She checked on the times of flights and she checked out the park where she was eventually found.
Yes, that could have been staged but her family wasn't surprised by her computer activity. Had it been staged, it would have meant that an intruder would have been in her apartment until something like one in the afternoon. That would have exposed any intruder to a high risk of detection--they couldn't depend on the security tapes not being requested until after they'd already been recorded over.
If Condit were responsible, it would have had to have been a professional hit. So why were Chandra's pants found knotted? Pro hit men don't play with their victims, they don't want to get any closer to a victim than they have to so as to leave as little evidence as possible.
Once it became publicly known that Chandra had a connection to Gary Condit, it would have been much to Condit's advantage for her body to be found promptly. There's plenty of ways the location of her body could have been revealed to the police without endangering the sender, so why wasn't it done?
I don't think Condit had a motive. The last communications from Chandra to her family (including the aunt she confided in) were reported to be upbeat, happy and planning for the future.
I think it's much more likely that Condit had led Chandra on or may have been a bit carried away in the passion of the moment. He was a serial adulterer, very experienced in letting women down gently once he was no longer interested. I think he was planning to let distance fade the connection that Chandra felt for him a bit, and then a final parting of the ways, as he'd done so many times before.
Considering his personal history, I think things would have gone as Condit was probably planning until something happened to Chandra.
I don't feel sorry for Condit, mind you. I think he was nearly terminally stupid and should not have lied to the police. But there's a lot of ground between terminally stupid and murderer which I do not think Condit crossed.