You may have seen the television ads for the presidential candidates, but what you're not seeing could count more in the end.

So, just how much will candidates have to invest to persuade voters all across the Lone Star State to vote their way.

In the ground war for president, one of the most effective ways to convey a message in politics is to hand out flyers and get face-to-face with voters.

And so are TV ads from Democratic presidential candidates Barack Obama and Hillary Clinton, whose campaigns began blanketing the airwaves across Texas Tuesday.

"It's going to cost several million dollars,” said Sandra Shafto.

And Shafto should know. She's spent more than a decade buying airtime for political, in a big state that's more like a small country.

In addition to Houston, the state of Texas has 18 television markets, two of them are in the top 10.

Each of them has unique demographics, which both the Obama and Clinton campaigns will try to master in a hurry.

“Just like there are people in different parts of the country concerned about different things, there are people in different parts of Texas concerned about special interests,” said Shafto.

The candidates only have until March 4 to hit the right note. Some political experts believe the candidates will likely play it safe.

"The few ads I've seen about Hillary Clinton, the tone is clearly about her, about her leadership, about her experience,” said 11 News political expert Bob Stein. "The good news for Obama, is that people are expecting this, they've heard about this hope, this new challenge, this change."

Which, said Stein, could transform viewers of political ads into voters when it matters most.