The second is guts. He's running even though established Republican leaders on Wall Street and in Washington fear or loathe him, or both. He casts them as just as removed from ordinary Americans as Democratic leaders—and he's willing to challenge them, too, in the name of conservative principles.
The third is that those principles include social conservatism. By announcing his candidacy at the Jerry Falwell-founded Liberty University, he's separating himself from Republicans such as Rand Paul and Chris Christie and Jeb Bush who want to play down social issues such as same-sex marriage as broader public opinion moves toward acceptance. Conservative Christians remain a powerful force in Republican primary politics—and especially in the Iowa caucuses that kick off the nominating process next February.
Read More Ted Cruz announces presidential bid
Can Cruz win the nomination? It's unlikely, considering how divided Republicans have become about the first-term Texas senator since he burst onto the national scene in 2012 and quickly agitated for a government shutdown the party had hoped to avoid.
In the most recent NBC News/Wall Street Journal poll, 42 percent of Republicans expressed willingness to consider backing him. But 40 percent did not. Gov. Scott Walker of Wisconsin, to take one notable example, fared much better.
Read MoreBrawl over budget will frame 2016 presidential race
Nor will Cruz be able to raise the vast sums that former Florida Gov. Bush, son of one president and brother of another, will command.
Yet Cruz boasts an immigrant's story (his family is from Cuba), a sharp debating style, and the attention-grabbing first mover's advantage in the race. He will command an audience and force rivals to either chase him to the right or make a point by refusing to.