Bill and Hillary Clinton to become grandparents, again

WASHINGTON -- There likely will be one more Clinton on the campaign trail next fall.

Chelsea Clinton, the only child of former President Bill Clinton and former Secretary of State Hillary Clinton, announced Monday that she is expecting her second child next summer.

"Charlotte is going to be a big sister! Feeling very blessed & grateful this holiday season," Chelsea Clinton wrote on Twitter.

Chelsea Clinton, 35, and her father have largely stayed off the campaign trail since Hillary Clinton launched her Democratic bid for the presidency in April.

Both have said they plan to intensify their public political roles after the New Year in an effort to boost Clinton's campaign just six weeks before the first round of primary voting.

The soon-to-be second-time grandparents tweeted out their congratulations Monday.

"Your dad and I could not be happier for you, Marc, and Charlotte. We're so excited to meet our second grandchild!" wrote Hillary Clinton.

Bill Clinton added: "Christmas comes early! HillaryClinton and I are thrilled for Chelsea, Marc and Charlotte's growing family in 2016!"

In a September interview on NBC's "Today," Chelsea Clinton said her mom was always game for singing "The Wheels on the Bus" to granddaughter Charlotte and was helping her learn to walk.

The younger Clinton is author of the book "It's Your World: Get Informed, Get Inspired & Get Going!" - an illustrated guide for young people looking to become involved in political and social causes.

Chelsea Clinton is married to hedge fund manager Marc Mezvinsky, the son of former U.S. congressman Edward Mezvinsky and former U.S. congresswoman Marjorie Margolies-Mezvinsky.