He has been in office for barely six weeks, but already the senator from Texas, a favorite of the conservative Tea Party movement, has shown a provocative, in-your-face style that has won him criticism and praise.
Cruz, 42, has been chided by Democrats and even fellow Republicans who say he trampled Senate etiquette during contentious hearings in which he went after former Republican Senator Chuck Hagel, Democratic President Barack Obama's nominee for defense secretary.
While some Republican leaders have sought to broaden the party's appeal with a more moderate tone on a range of issues, Cruz has unabashedly - and often dramatically - cast himself as a hard-line conservative with a distaste for compromise.
The question is whether this behavior will limit his effectiveness in the long run:
But some analysts said Cruz's confrontational approach also put him at risk of being marginalized and portrayed as a political bomb thrower in a gridlocked Congress.
"He talks about issues from an ideological perspective. But has shown no sign of being someone who could sit down and work out a solution to a complicated problem," said political scientist Cal Jillson of Southern Methodist University in Dallas.
Norm Ornstein, a congressional analyst at the American Enterprise Institute, said Cruz had been pushing the limits on standards of behavior in the tradition-bound Senate.
But the story points out how Cruz began his carreer and suggests that this helps explain his unusual influence within the chamber - at least among Republicans:
. . . Cruz, a Harvard Law School graduate who was a clerk for former Supreme Court Chief Justice William Rehnquist and served as Texas solicitor general, has also built bridges with more established Republicans eager to court the party's conservative wing and promote a rising Hispanic star.
Party leaders gave him a plum speaking slot at last year's national convention, and sought-after appointments to the Senate Judiciary and Armed Services committees once he was elected. They also made him vice chairman of the Senate Republican campaign arm, which will recruit and back candidates in the 2014 elections.
The top two Senate Republicans, Mitch McConnell of Kentucky and John Cornyn of Texas, both hope to avoid primary challenges from conservatives next year and have sought to strengthen their relationships with Cruz.
Cruz accompanied McConnell on a congressional visit to Israel and Afghanistan last month and won an admirer in the process. McConnell told the National Review Online afterward that Cruz was "ready for prime time on day one, which is pretty unusual for somebody who just got sworn in."
Meaning that he already has connections with the establishment and Tea Party wings of the party and is a broker between the two. The fact that two senior Republicans feel the need to cozy up to him suggests that he can help determine whether they will face a Tea Party Challenger in the primaries next year. So he may be calling some shots in the party This is clever.
