Democratic Sen. Tom Harkin's supporters went door-to-door with handheld computers this summer, questioning voters on their preferences. Each night, the dozens of volunteers downloaded their findings into a central computer site to chart the senator's popularity.

"We're building a nice little database," said Harkin aide Jeff Link, who plans to double the effort.

Harkin, a liberal Democrat who is chairman the Senate Agriculture Committee — a very big deal in the Farm Belt — got a scare in his last re-election effort. And he is already trying to make sure it doesn't happen again in 2002.

In 1996, Harkin won 52 percent to 48 percent over then-Rep. Jim Ross Lightfoot. But the senator and his aides concede they may have given up a giant early lead by not working harder earlier in the campaign.

This time around, Harkin will face Rep. Greg Ganske, a plastic surgeon from Des Moines, who began taking verbal potshots at Harkin even before his own re-election to the House last November.

The GOP has targeted the race as one crucial to regaining control of the narrowly divided Senate in 2002. The Democrats took a 50-49 lead when Republican Sen. James Jeffords of Vermont became an independent. The Republicans are defending 20 seats, the Democrats 14.

Many GOP strategists see Iowa — where there are 30,000 more registered Republicans than Democrats — as one of their best shots.

Al Gore carried the state last year, but only by 4,000 votes. Since then, President Bush has visited Iowa three times in hopes of bringing the state into his camp. He has also pledged to give Ganske all the help he needs.

No polls have been released on the Harkin-Ganske matchup.

Both sides have been laying the groundwork for months.

Harkin, 61, hopes to make gains in traditionally Republican rural Iowa by noting he is the first Iowan since 1910 to be chairman of the Agriculture Committee, while his opponent is from the city. The three-term incumbent also plans to emphasize issues such as Social Security and Medicare, both key in a state with a large elderly population.

For his part, Ganske, 52, plans to run as a Republican moderate, emphasizing issues such as health care and water quality that appeal to women and suburban moderates.

"I think my campaign presents a lot of problems for him," Ganske said. "Those are all important issues to swing voters."

Financially, the race is likely to be a draw.

Harkin spent $6.5 million to win his third term, and both candidates will probably top that number this time around.