Updated at 11:40 a.m. ET
Former President George H.W. Bush will formally endorse Mitt Romney for president on Thursday, CBS News has confirmed.
The former president has made supportive comments in the past about Romney, and his wife Barbara Bush has recorded robocalls for the candidate.
Mr. Bush will make the endorsement in Houston, where he's meeting with Romney. Neither former President George W. Bush nor former Florida Gov. Jeb Bush -- who has-- will be at the meeting.
Romney has long been considered the "establishment" candidate, but in the past month, more high-profile Republicans have indicated it's time for the GOP to finally coalesce around one candidate. As Romney continues to rack up delegates and his opponents continue to falter, anhas grown around his campaign. In addition to getting stronger support from the GOP establishment, Romney has seen his level of improve as well.
According to CBS News estimates, Romney has 554 delegates while Rick Santorum has only 241. Newt Gingrich has 128 delegates, while Ron Paul has 42. At this point, Romney's competitors seem to have more hope of simply preventing him from accumulating the 1,144 delegates necessary to win the nomination outright rather than actually getting the delegates themselves.
As he gets closer to securing the Republican nomination, Romney is pivoting his campaign to.
That doesn't mean his opponents are ready to throw in the towel, however. Even after the Gingrich campaign, the candidate is insisting he's staying in the race. Hours before that announcement, Rick Tyler, who runs a pro-Gingrich super PAC, told CBS News' Bob Schieffer on "Face to Face" that would prevent his candidate from taking his candidacy to Tampa.
CBS News Producer Caroline Horn contributed to this report.