But the Democrats, who need to challenge only nine incumbent Republicans, made no effort in four of those races.

After serving as a state senator, he defeated an incumbent Republican for a House seat in 1996.

Democrats think this is one of their best shots at unseating an incumbent Republican.

The idea seems to have worked; no incumbent Republicans lost on Tuesday.

An incumbent Republican is defending his seat against a Democratic challenger.

In 1948, he was elected to Congress, upsetting the incumbent Republican.

They give contributions to incumbent Republicans, too, and many also receive state contracts.

But as his own close call demonstrated, incumbent Republicans are at risk, too.

That year all the newcomers were Democrats, including five who defeated incumbent Republicans.

She lost narrowly; the two incumbent Republicans, both men, were returned to office.