He died in 1864 and his death created a leadership vacuum.

He will want to act quickly to calm investors concerned about a leadership vacuum.

Perhaps worst of all, there is a leadership vacuum at the top.

There are few hard numbers by which to gauge the cost of the leadership vacuum.

"There is a leadership vacuum in the region, and they have to step forward, or Iran will."

All of which, some say, points to a leadership vacuum.

But others in the party say the governor's problems have created a leadership vacuum that is likely to lead to other challenges.

But that could change if there was a leadership vacuum at the top.

California quickly jumped into the leadership vacuum with a robust $3 billion research program.

The leadership vacuum is big enough to suck in an entire black hole.