WASHINGTON (CNN) -- Ohio Republican George Voinovich on Monday will announce that he is retiring from the U.S. Senate, sources close to the senator told CNN.
The 72-year-old senator and former Ohio governor has been contemplating retirement for some time, but made his final decision this weekend in Florida, where he was joined by his wife, children and grandchildren, according to one of the sources.
Voinovich plans to serve out his term, which expires in 2010, sources said.
He plans to make the announcement at 4 p.m. Monday in Washington, the source said.
Voinovich will be the fourth Republican senator to announce he will not run for re-election in 2010. Sen. Kit Bond, R-Missouri, said late last week that we would retire, joining Sens. Mel Martinez of Florida and Sam Brownback of Kansas who had already announced they would leave Capitol Hill when their terms end at the close of the 111th Congress.
Republicans must defend 15 incumbents and four open seats in 2010. Sen. Kay Bailey Hutchison, R-Texas, whose term expires in 2012, is seriously considering a 2010 gubernatorial bid and could also be vacating her seat early.
Meanwhile, Democrats have to defend 15 incumbents and two seats for which special elections are expected to be held.
In Delaware, a special election will be scheduled for Vice President-elect Joe Biden's seat and New York will also hold one if Sen. Hillary Clinton is confirmed as the next secretary of state.
