Rick Santorum has  endorsed Texas U.S. Senate candidate Ted Cruz, announcing his backing of the former state solicitor general - and Tea Party favorite  - Thursday morning on the Glenn Beck radio show.

The former presidential candidate  praised Cruz,  calling him "spellbinding, a tremendous orator, and principled."

Former Alaska Gov. Sarah Palin and South Carolina Sen. Jim DeMint had already endorsed Cruz, who goes up against Lt. Gov. David Dewhurst - the front-runner - in the May 29 primary  to replace  retiring GOP Sen. Kay Bailey Hutchinson.

Dewhurst has been endorsed by Texas Gov. Rick Perry and former Arkansas Gov. Mike Huckabee. There are also two others running: the former Dallas Mayor Tom Leppert  and former football player and ESPN commentator Craig James.

"What we are missing in the United States Senate is not just a good conservative vote," Santorum told Beck. "But the skills and leadership to articulate the message … really engage the debate on the floor of the Senate … beyond just taxes and spending."

If neither candidate gets more than 50 percent in Tuesday's primary, the race goes to a runoff, which would take place  July 31. Polling shows Dewhurst ahead, but not at the 50 percent mark, so a runoff between Cruz and Dewhurst seems likely.

Santorum had strong support in Texas before abandoning his presidential bid. He campaigned several times to large crowds  and his super PAC held a fundraiser in Dallas that he attended in February.

The former Pennsylvania senator's campaign staff  tried feverishly to change the primary to a winner-take-all from a proportionate awarding  of delegates to try to win that state's large delegate  bounty. When that proved impossible, Santorum said that was one of the reasons he left the race  last last month.

ABC News' Elizabeth Hartfield contributed to this report.