Ronald Reagan's Eleventh Commandment - "Thou shalt not speak ill of any fellow Republican" -  has been left in tatters in the run-up to today's GOP primary in Texas.

Some of the campaigning has been truly nasty. That's particularly been the case in the race for the senate seat of retiring Kay Bailey Hutchison. The two frontrunners, Lt. Governor David Dewhurst and former Texas Solicitor General Ted Cruz, have called each other liars in television ads.

Some observers say the attack ads are part of a "blood sport" political culture in Texas, while others say the personal attacks have been the invariable consequence of conservatives -- who differed little politically -- trying to distinguish themselves from their opponents.

One theme pervading all of the campaigns: Who is the most conservative in red state Texas?

As Associated Press reporter Chris Tomlinson explains in an insightful article:

The story line on the Republican Senate race in Texas is a now familiar one: A veteran politician supported by the GOP establishment is challenged by a young insurgent backed by national conservative groups.

In this distinctly Texas episode in the saga for control of the Senate, David Dewhurst is the reserved, self-made millionaire and lieutenant governor facing off against Ted Cruz, the feisty son of a Cuban exile who calls himself "a proven fighter for liberty because his family knows what it means to lose it."

The underdog is former Dallas mayor and businessman Tom Leppert, who offers himself as the no-nonsense alternative to politics as usual.

In heavily Republican Texas, whoever wins the GOP primary on Tuesday is almost sure to replace retiring Sen. Kay Bailey Hutchison.

Regarding the ugly attack ads, another Associated Press article by Tomlinson observed that "Both campaigns are guilty of exaggeration and spinning the facts, though there are tiny elements of truth in the accusations."

Texans were bombarded in particular by two attack ads - one portraying  Dewhurst as - yikes! - a "moderate" Republican. The other portrayed Cruz as an unscrupulous trial lawyer.

For an idea of what voters in Texas have been subjected to on television in recent weeks, click here and here. Ronald Reagan must be rolling over in his grave.