U.S. Senator Ted Cruz (R-Tex.) delivers his remarks at the morning plenary session of the Values Voter Summit in Washington September 26, 2014. (Gary Cameron)

Sen. Ted Cruz (R-Tex.) will campaign for Sen. Pat Roberts (R-Kan.) later this week, Roberts's campaign announced Monday. The tea party star becomes the latest well-known Republican to join the effort to rescue Roberts, who polls show is trailing independent candidate Greg Orman.

The Texas senator will help launch a Roberts campaign bus tour on Thursday. Sen. Tom Coburn (R-Okla.) will also join the effort.

"To stop the liberal Harry Reid-Barack Obama agenda, we must win the Senate Majority – and we can’t do that without Pat Roberts back in the Senate," Cruz said in a statement.

An NBC News/Marist poll released Sunday showed Roberts trailing Orman by 10 points. Orman has not said which party he would caucus with if the majority comes down to him.

Roberts is trying to shore up his support among Republicans of all ideological persuasions in the closing weeks of the campaign. He's already brought in Sen. John McCain (R-Ariz.), Sarah Palin and former Senate majority leader Bob Dole to stump with him.