At a Tea Party rally in Austin on Sunday, Ron Paul and his son, U.S. Sen. Rand Paul, R-Ky., gave ringing endorsements to Cruz's bid to replace U.S. Sen. Kay Bailey Hutchison. Ron Paul urged Texans at the event to "send Ted to the Senate because Rand needs help."
While former Massachusetts Gov. Mitt Romney is the presumptive Republican presidential nominee, Paul has not ended his campaign and is focused on drawing as many delegates as possible to this summer's national Republican convention.
Last year, Cruz endorsed Gov. Rick Perry for president. Since Perry has ended his bid, Cruz has echoed many other Texas Republican candidates in declining to back a second candidate.
"Because it is critical to defeat Barack Obama in November, Ted will enthusiastically support the Republican nominee," Cruz campaign manager John Drogin said Monday.
"Throughout this campaign, Tom has said stated repeatedly that he would vigorously back the Republican nominee," said Daniel Keylin, a spokesman for Leppert. "Tom will be working nonstop to ensure that Mitt Romney defeats Barack Obama in November."
James had previously endorsed Rick Santorum, who suspended his presidential campaign last month.
"Craig has stated at several events in the last few weeks that he is supporting the Republican nominee, which will most likely be Mitt Romney," spokeswoman Meredith Turney said. "Craig's committed to ensuring Obama is not re-elected, and that means being a Republican team player supporting the nominee, Mitt Romney."
Turney added that James is hopeful Romney will pick Santorum as a running mate.
Lt. Gov. David Dewhurst has not responded to a request for comment.