Explainer: Here's how political campaigns got your phone number

In the final stretch of a heated runoff between Gina Ortiz Jones and Rolando Pablos , text messages are flying from campaigns and the outside groups supporting them.

Political strategists say texting has grown in popularity as a relatively cheap way to contact voters — costing roughly 5 to 7 cents per message — though opinions vary on their efficacy as a campaign tool.

“Text messages are the 21st century robocall,” said San Antonio political strategist Kelton Morgan, whose firm CSG Campaigns specializes in direct voter contact and print mail. “They’re cheap, and for a lot of broke campaigns, that’s what they can afford to do.”

Of the nearly $1.7 million reported campaign expenditures in the runoff, Jones and her allies have been outspent about three-to-one .

San Antonio political