Correction, McCain used to be a maverick. In this election cycle, to put himself more in line with the party, he has flip flopped on:

Bush tax cuts
Drilling off shore
Ethanol
Gay marriage
Roe v Wade
Displaying the Confederate flag
A timetable for withdrawal from Iraq
Privatizing Social Security
Kissing the religious right's butt (remember when he called Falwell and Robertson "agents of intolerance")

This is just a partial list, but though the McCain campaign continues to try and market him as a maverick, it demonstrates quite clearly he is just a plain old party line Republican.