By LESLEY CLARK

Lincoln Diaz-Balart is reviewing the paperwork a staffer has put before him, but his mind is elsewhere -- on a conversation he wishes he could have with his late father.

''I wish my dad were still alive,'' he muses, reflecting on the passion for history and politics instilled in him by Rafael Diaz-Balart, the charismatic patriarch and Cuban legislator.

For Lincoln Diaz-Balart, 54, a Cuban-born child of exiles, his future and present are almost always entwined with the past. A dedicated patron of the Library of Congress, he is rarely without a stack of historical and political biographies on his desk. It sharpens and informs his decision-making, he says.

''We've all got to have a hobby, no?'' he says.

But his emphasis on history goes to the heart of criticism against him: that he is wed to the past, in particular to Cuba. When Congressional Quarterly, a publication that covers Capitol Hill, named Diaz-Balart one of the 50 most effective members of Congress in 1999, it nevertheless called him a ''niche player,'' noting that ''to his colleagues and constituents, he is known, first and foremost, for his crusade against Castro's Cuba.'' Critics say little has changed nearly a decade later.

At times, the crusade is explosive. In 1995, Diaz-Balart was arrested outside the White House while protesting President Bill Clinton's Cuba policy. Just a year after his 1992 election to Congress, he took retribution on a lawmaker who had cut Radio and TV Marti's budget. Diaz-Balart slashed millions more from a project in the Colorado lawmaker's district.

Now, facing the first real challenge to his seat from a populist Democrat who says today's voters are more worried about home foreclosures than Cuba policy, Diaz-Balart is campaigning aggressively and raising more money than ever.

As of Aug. 6, he had raised $1.7 million, about a quarter of it from law firms, real-estate interests and political action committees with interests in foreign and defense policy, according to the Center for Responsive Politics, a nonprofit, nonpartisan group in Washington.

Yet, even some Republicans in his district say Diaz-Balart remains a bit of a mystery.

''Most people don't know what it is he's been doing all the time he's been up there,'' said Robert Bueso, a Republican and treasurer of the East Kendall Homeowners Organization. ``We do know his opinion on Cuba.''

`AN INSULT'

Diaz-Balart's focus has prompted accusations that, as the premier defender of U.S.-Cuba policy, he views his seat in Congress as a stepping stone to the job he really wants: president of Cuba.

Diaz-Balart, who wears a wrist bracelet with the word cambio -- change -- to show solidarity with Cuban dissidents, finds the assertion offensive.

''That's an insult to those who today are in Fidel Castro's dungeons,'' said Diaz-Balart, whose aunt was once married to Castro. ``Those are the heroes of Cuba. Those who have given their freedom, their blood, they are the ones who have earned the presidency.''

The race and its potential to change the tenor of U.S.-Cuba relations is drawing national attention, and Diaz-Balart is seeking to broaden his appeal. When interviewers ask about his proudest accomplishment, he doesn't start with his role in seeing that the U.S. embargo against Cuba was enshrined into law.

Instead, he touts a 1997 law that prevented an estimated 150,000 Nicaraguans from being deported. A photograph on the credenza in his office bears witness: the lanky congressman greeted as a hero in Miami by a cheering Nicaraguan crowd.

Frank Sharry, an immigration advocate long accustomed to battling various Republican efforts to restrict immigration, calls Diaz-Balart his ``favorite Republican.''

''He's consistently a champion, which has been consistently difficult given that he's in a party where the majority isn't with him,'' Sharry said, crediting Diaz-Balart with getting significant legislation passed. ``There's a lot of folks who will show up at the press conference. It's something else to use your political capital to make it happen.''

NOT THE PARTY LINE

Immigration is one area in which Diaz-Balart, a generally reliable Republican vote, has shown flashes of independence. He includes passage of ''fair and sensible immigration legislation'' as one of his priorities for another term. Other top issues: boosting jobs and federal dollars for South Florida, strengthening the economy, ``protecting freedom, and working to expand it to where it is lacking.''

In 1994, Diaz-Balart took exception to a plank in the Republican Party's Contract with America -- the centerpiece of GOP efforts to take back the House of Representatives that year. The measure he opposed called for cutting off benefits to legal immigrants. Retribution within the party can be swift: no significant committee assignments, no action on legislation.

Diaz-Balart became one of just three holdouts on signing, and says he never looked back. And he rounded up his South Florida colleague, Rep. Ileana Ros-Lehtinen, to share his misgivings: 'I found Ileana at midnight and said, `We can't sign this,' '' he said.

The party didn't hold a grudge: He was later appointed to the House Rules Committee, which plays a key role in determining what legislation gets to the floor for a vote. Diaz-Balart, the second most senior Republican on the panel, says he has used the position to get key bills passed.

He cites the decision to reject the party contract as proof that he doesn't always toe the party line. Indeed, his voting record during this session shows him siding with the Democratic majority on a number of issues, including a bill President Bush opposed to allow housing authorities to buy foreclosed properties with federal dollars and resell them to low-income families.

WHO GETS THE CREDIT?

Diaz-Balart was one of just 11 Republicans to back the measure, and his opponent, former Hialeah Mayor Raul Martinez, called it a ''campaign victory'' for himself.

Diaz-Balart said he wasn't aware that Martinez had called on him to vote for the legislation, and he mocked what he sees as his rival's effort to take credit.

Among other accomplishments, Diaz-Balart touts the securing of $10 million for the Ryder Trauma Center at Jackson Memorial Hospital and $5.5 million for snazzy new buses for Miami-Dade County. This month, he twice voted against Bush's Wall Street bailout plan; Martinez, too, said he opposed the measure.

Martinez suggests an election-year conversion and dismisses Diaz-Balart as a rubber stamp who backed Bush in the Iraq War, opposed efforts to impose a timeline for a troop withdrawal, and supports the Bush tax cuts. In its latest rankings, the Family Research Council scores Diaz-Balart at 71 percent for the number of times he sided with that conservative group; the environmentally minded League of Conservation Voters gave him a 17.

But Diaz-Balart isn't always so easily typecast. His best friend on Capitol Hill has long been a Democrat -- New Jersey Sen. Bob Menendez, a son of Cuban exiles, who dined weekly with Diaz-Balart when the two were in the House and who attended Rafael Diaz-Balart's funeral in 2005.

And Diaz-Balart, whose first job after law school was with Legal Services of Greater Miami, was once a Democrat. Enthralled by Ronald Reagan's tough talk on communism, and disenchanted with the Democratic Party, he, his wife, Cristina, and brother, Mario, switched parties in 1985. The following year, he was elected to the Florida House.

Through it all, he has not lost the zeal -- and the aggression. Diaz-Balart's first television ad this campaign opened with soaring music and positive rhetoric about the incumbent. Then it went straight for Martinez's jugular, accusing him of a history of ``insults and vulgarities.''

Cruising through the Capitol recently, Diaz-Balart outlined his approach as he exchanged pleasantries with New York Democratic Rep. Charles Rangel -- one of his nemeses on Cuba policy.

``Lo cortés no quita lo valiente,'' Diaz-Balart wrote in a reporter's notebook after the two chatted amiably.

Loosely translated: ``You lose nothing by being polite.''