(CNN) - Clint Eastwood will be the "mystery guest" at the Republican National Convention's final night, a GOP source confirmed Thursday.
Eastwood, a longtime Republican, is expected to walk through the convention floor in the afternoon for a brief rundown of the night's events.
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The actor endorsed Romney at an Idaho fund-raiser at the beginning of August, where he told reporters beforehand he was backing the Republican presidential candidate "because I think the country needs a boost somewhere."
He later told hundreds at the outdoor reception that Romney was "going to restore, hopefully, a decent tax system that we need badly...so that there's a fairness and people are not pitted against one another as to who's paying taxes and who isn't."
Convention organizers had been teasing a surprise "mystery guest" all week at the convention in Tampa but would not give details or hints about the surprise speaker.
Romney will accept his party's nomination for president Thursday night.
- CNN Political Producer Shawna Shepherd contributed to this report.