WASHINGTON – Senator McCain, the straight-talking Republican who often challenges the GOP establishment, has taken on a headline-grabbing issue – steroids in baseball – and generated talk of a presidential bid in 2008.

Amid revelations about baseball’s biggest names, Mr. McCain has threatened to push legislation early next year if Major League Baseball and the players do not clean up their act. Mr. Mc-Cain long has advocated harsher penalties for athletes caught using performance-enhancing drugs.

The three-term senator from Arizona has earned a reputation as a go-to lawmaker, tackling campaign finance, the war on Iraq, federal spending, and climate change.

It’s little wonder that his foray into the baseball scandal has revived Republican speculation about Mr. McCain and the 2008 presidential race.

Even though President Bush has yet to take the oath of office for a second term, other names that have surfaced as possible GOP candidates in 2008 include Dr. Bill Frist, the Senate majority leader of Tennessee; Senators Hagel of Nebraska, Allen of Virginia, and Santorum of Pennsylvania; Rudolph Giuliani, the former New York City mayor, and Governors Romney of Massachusetts and Pataki of New York.

“The big question is: Can McCain get any hotter?” said Scott Reed, a Republican consultant.

The talk is coming from outside the Washington beltway, too.

“He’s pretty well set to go in four years,” said Jerry Roe, a former head of the Michigan Republican party. “Politicians that go anyplace are like rock stars. McCain’s a rock star.”

A senator since 1986, Mr. McCain sought the GOP nomination in 2000 but lost to Mr. Bush in a bitter campaign. Over the next four years, Mr. McCain, a former Vietnam prisoner of war and deficit hawk who rarely held his tongue, became a frequent critic of the Bush administration and gained a reputation for bipartisanship.

This year, Mr. McCain showed his loyalty to the Republican party when he campaigned for the president and rejected overtures from his Democratic friend and Senate colleague, John Kerry of Massachusetts, to run for vice president on a bipartisan ticket.

Mr. McCain stirred the pot throughout, defending Mr. Kerry when his patriotism was questioned and criticizing the president’s foreign policies. Mr. Mc-Cain’s actions drew widespread media coverage and heightened speculation that Mr. McCain was setting himself up for his own 2008 bid.

Mr. McCain deflects questions about another run for the White House.

“I have no contemplation for the next couple of years to do anything except be a good senator,” Mr. McCain said last week on CNN. “I don’t think I can help the people of Arizona by planning and plotting to be president of the United States when the present president hasn’t even been inaugurated for a second term.”

Still, he leaves the door open.

His Senate re-election campaign Internet site links Web surfers to an online store that sells his books, T-shirts, pins, and tote bags emblazoned with “Straight Talk Express,” the slogan from his 2000 presidential bid.

Mr. McCain has not established a political action committee or latched onto the fund-raising circuit in early primary states. Then again, he does not have to. He’s making waves just by “being McCain,” say several Republican strategists and political analysts.

“He’s such a unique personality, and he’s one of the few United States senators who has a national constituency,” said Marshall Wittmann, Mr. McCain’s former communications director who became a Democrat this year. He suggests that Democratic Senator Clinton of New York and perhaps Senator Kennedy of Massachusetts may be the only others.

“Anything they say on an issue, people take note. And, if it wasn’t an issue before, it’s made into an issue,” said Mr. Wittmann.

That’s why, analysts say, Mr. McCain will not lose his bully pulpit when he steps down as chairman of the Senate Commerce, Science, and Transportation Committee in January.