McCain, who's celebrating her 36th birthday on Oct. 23, gave birth to baby girl Liberty Sage McCain Domenech Monday evening.
"Thank you all from the bottom of my heart for all the wonderful well wishes and overwhelming kindness. Ben and I are completely and utterly in love with our daughter and feeling indescribably blessed/blissed out," McCain tweeted Tuesday afternoon.
"We will be watching her first debate as a family together tonight!" McCain continued.
McCain and Domenech married in November, 2017 and announced their pregnancy on March 22.
"My husband Ben and I have been blessed to find out I'm pregnant," McCain wrote in her announcement on Instagram. "Although this isn't how I expected to announce my pregnancy, both we and our families are excited to share the news with you all."
Her news came as the country grappled with the seriousness of the novel coronavirus outbreak. While in good health, McCain co-hosted "The View" via satellite under her doctors' advice since March.
Throughout her pregnancy, McCain has been candid about the struggles of being an expectant mother.
"Every woman who has ever been pregnant deserves a medal of recognition!!" McCain tweeted on Sept. 14.
"The struggle is real," an eight-months-pregnant Meghan McCain said in an Instagram caption on Aug. 26. "Any tips on how to get comfortable sleeping, swollen feet or anything else from all the women who have been down this road would be greatly appreciated!"
On July 2, McCain shared a throwback photo of her and husband Domenech on Instagram expressing how grateful she is for his attention to her during her pregnancy. "#TBT to when we could still go out to dinner. We’re so lucky, Ben," she said in the photo caption. "Thank you for taking such wonderful care of my bloated, knocked up, swollen, pandemic navigating self. I don’t know what I would do these days without such a strong, loving partner."
Both the mother and baby Liberty are healthy and doing well.