Ted Cruz is running scared.

The incumbent U.S. senator won't view that as an insult. His style is campaigning as if he's 20 percentage points behind, not the favorite in what's been a reliably red state.

U.S. Rep. Beto O'Rourke is clearly a legitimate challenger, much different than Cruz's 2012 general election foe, former state Rep. Paul Sadler. O'Rourke is raising more money than Cruz and the former punk rock musician has become a pop sensation, particularly in Texas Democratic politics. He's playing to large crowds in every corner of the state.

Cruz has taken notice.

His proposal to debate O'Rourke five times cuts against the strategies of most Texas Republican incumbents. Most statewide GOP nominees aren't debating their rivals at all. The one who has agreed to debate, Gov. Greg Abbott, wants a single forum at an obscure time.

Not Cruz.

So what does it mean that an incumbent wants to debate his challenger so frequently, even in a state that has been solidly Republican?

Cruz knows better than most Texas politicians the perils of ignoring a rival on the rise. He realizes that O'Rourke isn't going away, and the best way to beat the political upstart is to motivate the conservative base. Winning involves not hiding from competition or sitting on a lead.

In 2012 Cruz was the underdog in a GOP primary for Senate, where he started out with low name recognition and running at 2 percent support in most polls.

The frontrunner in that race was David Dewhurst, then the lieutenant governor and a veteran of three statewide campaigns. With polls showing him ahead, Dewhurst made a strategic decision to skip numerous debates and forums held by grassroots organizations and the bourgeoning tea party movement.

As a challenger, Cruz attended nearly every forum, exchanging ideas with little-known candidates like Lela Pittenger, Glenn Addison and Curt Cleaver. There was also Dallas Mayor Tom Leppert and former Southern Methodist University football standout Craig James.

Dewhurst won the first round of the primary with a big lead, but it was clear Cruz had the momentum.

"If I make the runoff, I will beat him decisively," Cruz told me the day before the primary.

Congressman Beto O'Rourke speaks to supporters during a town hall at the Historic Santa Fe Train Depot in Gainesville, Texas, Saturday, June 9, 2018. He has now visited all 254 Texas counties since announcing his candidacy last year to unseat U.S. Sen. Ted Cruz. (Jae S. Lee/The Dallas Morning News) (Jae S. Lee / Staff Photographer)

By the time Dewhurst and Cruz had their one debate (I moderated it with then WFAA-TV (Channel 8) political reporter Brad Watson), Cruz was cruising.

The earlier forums allowed Cruz to build his name recognition and make the grassroots connections that allowed him to win the Senate seat.

More importantly, the former Texas solicitor general respected the process, knowing that in a low-voter turnout state, grassroots activists and their programs matter.

For this race, O'Rourke has been a marvel, and it would be risky for Cruz to take him for granted.

If there are indeed five debates, it will be a must-see event. Cruz is a seasoned debater, though he struggled trying to unravel Donald Trump when they clashed during the 2016 presidential primaries.

We don't know how O'Rourke will fare. His charisma and knowledge of the issues already makes him compelling.

The Senate showdown will be the most watched contest on the November ballot. Thanks to Cruz and O'Rourke, voters should have enough information to make an informed decision.