According to Axios, he will make the announcement later this morning. It could have major political repercussions:
One of Washington’s best-wired Republicans said:
“This is a Titanic, tectonic shift. … This is going to make every Republican donor believe the House can’t be held.” The announcement will help Senate Majority Leader Mitch McConnell (R-Ky.) in his fundraising because “the Senate becomes the last bastion,” the Republican said.