AUSTIN – He hasn't said he's running, but former Tennessee Sen. Fred Thompson has catapulted near the top of the field of presidential candidates favored by Texas Republican voters, according to a new poll.

Former New York Mayor Rudy Giuliani is the first choice of likely GOP primary voters in the survey by Baselice & Associates.

But Mr. Thompson, a conservative who's now an actor on the television show Law and Order, is tied for second place with Arizona Sen. John McCain.

Pollster Michael Baselice said Mr. Thompson's strong showing comes even though he's not as well-known as his top Republican rivals.

"He's got only half the people who can even form an opinion of him and already he's tied for second," said Mr. Baselice, a veteran GOP pollster not working for any of the candidates. "And he's not even announced."

According to the poll, 24 percent would vote for Mr. Giuliani if the 2008 Texas GOP primary were held today. Mr. Thompson and Mr. McCain were each the choice of 19 percent of likely voters, followed by former House Speaker Newt Gingrich at 12 percent. Mr. Gingrich hasn't announced that he'll run, either.

The survey of 831 likely Republican voters selected at random was conducted April 16-19. The margin of error is 3.4 percentage points.

Mr. Baselice noted that support for Mr. Giuliani, Mr. McCain and Mr. Gingrich has eroded since January.

Former Massachusetts Gov. Mitt Romney's support in Texas has risen slightly in the last three months. He's the choice of 8 percent of GOP voters, up from 6 percent in January.

Mr. Thompson was not in the January survey.

Kathy Haigler, a member of the State Republican Executive Committee from Deer Park, said she would like to see Mr. Thompson become a candidate.

"We're hoping and praying he's going to enter the race," she said.

Although some Republican activists say they are lukewarm about the GOP front-runners, the survey suggests that Republican voters generally like the field.

According to the poll, 77 percent have a positive impression about Mr. Giuliani and 9 percent a negative impression. Mr. McCain and Mr. Gingrich are positively viewed by about two-thirds of GOP voters.

Mr. Thompson and Mr. Romney are the least known, but both are overwhelmingly viewed positively by voters.