After lying all but dormant for months, two hot potatoes of Texas politics -- race and Enron -- have burst into the contest to fill the state's open Senate seat, one of the nation's most closely watched campaigns.

Perhaps it was inevitable. The Democratic nominee, former Dallas mayor Ron Kirk, is the first southern African American since Reconstruction with a plausible shot at being elected to the Senate. The Republican nominee, Texas Attorney General John Cornyn, has been a ranking public official in a state rocked by the meltdown of one of its leading companies, Enron Corp.

On Friday night, both themes got a prime-time airing when the candidates -- each a buttoned-down lawyer and pro-business moderate -- faced off here in a televised debate, the first of three scheduled this week and next. The result was a handful of sharp exchanges in which the candidates used racially tinged references to tweak each other, in addition to accusing one another of benefiting from Enron's cash before the energy-trading giant began to collapse last year.

On race, Cornyn rapped Kirk for attending a hip-hop "summit" last weekend in Dallas featuring a rap artist who worked on an album by the group N.W.A. that included the song "[Expletive] tha Police." Kirk pleaded ignorance about the song, which he said was recorded 14 years ago, and said he had attended the hip-hop event simply to urge young blacks to vote. He returned fire by saying Cornyn, as a high school student, had written an article in favor of George Wallace, the segregationist governor of Alabama who ran for president four times.

"The truth is, I was a Nixon man back in high school," said Cornyn. He said he had written about Wallace as a school assignment.

The two also tried to tar each other with the Enron brush, a strategy they adopted in TV ads this week. Kirk accused Cornyn of accepting $193,000 in political contributions from Enron executives when he ran for attorney general and then rewarding them last year by ruling that the firm could keep certain financial information secret. "You basically served as in-house counsel to Enron," said Kirk. "The bad news is the people of Texas were paying you at the time."

Cornyn, who later donated $200,000 to a fund for laid-off Enron employees, said his ruling complied with the law. He demanded to know how Kirk could attack him on this issue when the Democrat's own law firm had accepted $180,000 in legal fees from Enron. Kirk, who received only a small fee as mayor of Dallas, has continued to draw an annual salary of $227,000 from the law firm, Gardere Wynne Sewell, although he did no work on Enron's behalf.

Neither candidate appeared to land a knockout blow, but Cornyn kept Kirk on the defensive while crisply parrying the Democrat's charges. Kirk had trouble answering questions or offering rebuttals within the allotted 60- and 30-second slots, and once or twice appeared rattled. At one point Kirk, who seems slightly uneasy discussing foreign affairs, suggested that Saudi Arabia might develop weapons of mass destruction, a remark he had to modify in the post-debate spin session with journalists.

Even if the debate was a draw, as some analysts suggested, that may be bad news for Kirk. A Democrat in an overwhelmingly Republican state, he was a popular mayor and retains broad support in Dallas, even among Republicans who regard him as affable and pragmatic. But Kirk's considerable charisma does not come across so clearly on television or at large campaign events, where he sometimes seems formal and unfocused. Badly outspent by the GOP, he has lagged in the polls.

And today, a new statewide survey posted on the Dallas Morning News Web site suggested the gap is widening, with Cornyn leading 47 to 37 percent, and 14 percent undecided. The poll, conducted by the New York firm Blum and Weprin Associates Inc., had a margin of error of plus or minus 3 percentage points.

Just as dispiriting for Texas Democrats, the poll showed an even bigger Republican edge in the race for governor. Democrat Tony Sanchez, a Hispanic American oil and gas multimillionaire who has self-financed one of the most expensive races in state history, trails Gov. Rick Perry, the Republican who succeeded George W. Bush. Perry led, 50 to 35 percent.

President Bush, of course, has a keen interest in both races. He soon will visit his home state for the third time in four months to campaign for Cornyn in addition to having sent his wife, mother and vice president to stump for the Republican.

Democrats had hoped that Kirk and Sanchez would form the heart of an ethnically diverse "dream team" slate of statewide candidates. And much still depends on turnout among African Americans and Hispanics, which together constitute more than 40 percent of Texas population but have lately accounted for less than 30 percent of the vote.

If Sanchez or Kirk catches fire in the campaign's closing weeks, those core constituencies could go to the polls in numbers that conceivably might offset the Republicans' massive edge with white, Anglo voters.

"Ultimately this election was always going to be about the mechanics of turnout," said Harvey Kronberg, editor of the Quorum Report, an online newsletter of Texas politics. "The two major question marks are: Is the get-out-the-vote effort of Democrats as well organized as it's been promoted? And will Latino voters vote for an African American?"

The first of three debates brings together the two Senate candidates in Texas, Republican John Cornyn, left, the state attorney general, and Democrat Ron Kirk, former mayor of Dallas.