A former chief of staff for President George W. Bush warned Wednesday that Mitt Romney "can't coast to victory. He has to earn the victory."
Andrew Card made the comments on "CBS This Morning" the day after Romney won the GOP primaries in Arizona and Michigan.
"I think Mitt Romney has the momentum and is likely to be the Republican nominee," Card said.
"This is uncharted territory for the Republican Party. We don't have winner-take-all-primaries in every state the way we used to. This process was designed to play out for a longer period of time, and it will. "
Card hopes the GOP will come together and focus on the real mission -- to "make sure the White House will not be held by the Democrats for a long time."
To see the interview with "CBS This Morning" co-hosts Charlie Rose and Gayle King, which also included CBS News chief Washington correspondent and "Face the Nation" host Bob Schieffer, click on the video in the player above.