McCaskill, typically a prolific tweeter, had not tweeted since Monday night.

Just two weeks from Election Day and in a hotly contested Senate race, McCaskill canceled campaign events until the end of the week in order to stay with her 84-year-old mother, who's in the intensive care unit of a St. Louis hospital.

Her opponent in the Missouri Senate race, Rep. Todd Akin (R-Mo.), tweeted that he is praying for McCaskill. His tweets since then have not softened their political rhetoric, continuing to blast McCaskill's record on taxes and the Benghazi attack.

McCaskill is leading Akin in the polls.