On a crisp October afternoon, Ken Mehlman, the smiling, intense chairman of the Republican National Committee, greeted volunteers hunched over phones at Sen. Rick Santorum's Green Tree campaign headquarters.

After a quick interview with reporters, he'd head north to Melissa Hart's office to rally more GOP workers. The information that their calls have been gathering would be fed into a sophisticated voter tracking bank that Mr. Mehlman has helped nurture in his years at the RNC and, before that, as White House political director.

"I've got a huge investment, a multimillion-dollar investment, in voter turnout here," Mr. Mehlman said. "There's no state that I know of that has a more technically and technologically proficient turnout effort than here."

The next Saturday, the weather had turned cold and rainy, but that didn't deter about 80 union members from gathering in the United Steelworkers headquarters, Downtown, to get their voter lists, computer maps and scripts for a day of door-knocking at labor households.

A few floors above, Chuck Rocha, the union's political director, proudly showed off a roomful of computer terminals that can dial and deliver phone messages by the thousands from live human beings or from recorded calls.

"This is our new baby," he said pointing to the classroom-size phone bunker.

Elections are contests of candidates and ideas, but, at their sometimes decisive margins, they are also competitions of logistics, using tools as complex as computer algorithms and as basic as shoe leather. Once, unions such as the United Steelworkers were the gold standard for voter identification and get-out-the-vote efforts. In the past few election cycles, analysts of both parties agree, the Republicans have leap-frogged a tactical generation ahead of Democrats in their embrace of modern marketing and consumer identification technologies.

"I don't think we've completely caught up yet, but I think we've caught up a lot from 2004," Gov. Ed Rendell said, "But, of course, it's a concern."

Vince Galko, Mr. Santorum's campaign manager, has said that he is convinced that the GOP's turnout machine could be worth as much as five or six percentage points on Election Day.

Tuesday's results will suggest an answer to the question of how far the Democratic catch-up effort has traveled. That's just one of the questions surrounding the rival turnout efforts.

Changes from 2004

There were more votes cast for president in Pennsylvania in 2004 than ever before in an election in which both parties invested heavily in the most intensive and effective turnout efforts the state had ever seen. But the parties used very different models for their get-out-the-vote machinery.

On the Democratic side, there were the traditional cadres of organized labor, but the Kerry-Edwards ground effort also was heavily dependent on third-party groups with independent funding, such as Americans Coming Together.

Labor's still there and groups such as MoveOn.org and the Sierra Club have turnout operations that will aid Democratic candidates, but the big ACT apparatus, with its large, paid staff, is gone. To fill that political vacuum in Pennsylvania, Mr. Rendell's campaign has invested heavily in building the turnout operation of the Democratic Party's coordinated campaign.

"We've got a good turnout plan all over the state," Mr. Rendell said. "Some of our consultants are the same people who led the ACT effort in [the presidential race], so I think we're in better shape, turnout-wise, than we were in 2002."

The Republicans, in contrast, relied on community-based networks of thousands of unpaid volunteers in 2005. A significant potential advantage for the Republicans this time is that those volunteers, for the most part, are still in place.

The question on the GOP side isn't so much one of mechanics but of morale, whether, in a season of difficult news for their party, the Republican volunteers will have the motivation to be the potent force they were two years ago.

A variety of polls have suggested in recent months that, in contrast to 2004, Republican voters in general are less interested and less enthused about voting in this election than Democrats. An analysis by the survey firm Rasmussen Reports this week said, "the number of people identifying themselves as Republican has fallen to its lowest level since we began reporting measures of partisan trends in 2004."

When asked about polls suggesting an intensity advantage for Democrats this year, Mr. Mehlman said, "There are data points that indicate that. But there are just as many data points that indicate that the opposite is true."

Contrary to many predictions, the RNC chairman insisted that he was confident that the GOP, despite some losses, would retain control of both chambers of Congress.

Whether that proves true, there seems to be little question that the GOP grass-roots efforts rest on a more advanced technological foundation. The GOP didn't pioneer the concept of tailoring niche messages based on consumer buying habits. Commercial marketers have been doing that for a generation. But the RNC saw the political potential of melding the public information on voter registration lists maintained by governments with consumer information compiled by private commercial database firms.

'Micro-targeting'
Mr. Melhman described the kinds of insight that so-called "data mining" produced in a 2004 post-election speech before the Republican Governors Association. "If you drive a Volvo and you do yoga, you are pretty much a Democrat," he said. "If you drive a Lincoln or a BMW and you own a gun, you're voting for George Bush."

The buzzword is micro-targeting. Mr. Mehlman said that, by matching data on the buying habits and interests of GOP voters to nonvoters with similar profiles, the GOP was able to prospect for likely new supporters for its candidates.

Mike Podhorzer, the deputy political director of the AFL-CIO, is the micro-targeting maven for the labor group's voter effort.

"What micro-targeting lets us do is personalize what we say to people," he said. "People appreciate hearing the information they need rather than some cookie cutter type of thing."

He said the chief databases for the labor group's message segmentation was derived from voter rolls, census data and the results of large surveys of union households, such as one conducted in Pennsylvania in May.

"We take that information and look at a large database ... how often people vote, the kind of neighborhood they live in, their age, life situation. [We] use all the pieces of information we have about a person, and that helps us devise a strategy of personal communication."

Mr. Podhorzer is mildly skeptical of Mr. Mehlman's Volvo vs. BMW example.

"What car you drive and what liquor you drink can be significant, but things like age, race, religion are more consistently helpful in looking at voting behavior," he said.

He's not skeptical of the power of the overall GOP database effort, however.

"It's just simple election technology, but one of the main advantages the Republicans hold is that they've been doing it longer than we have," he said.

The GOP has set the standard for their opponents, not only in high-tech data collection but also in more informal, personal efforts to corral information.

"One of the things that gave them a huge leg up is the time they have spent reaching out to collect information they knew to be relevant, having their volunteers concentrate on collecting gun club lists, church membership lists," Mr. Podhorzer said. "Democrats have been much less aggressive in collecting those kinds of lists."

The AFL-CIO official said the Republicans had reaped an advantage from having a traditionally more centralized approach to voter identification and get-out-the-vote data. For the GOP, the data from a wide variety of sources is aggregated in the RNC's vaunted Voter Vault. Parallel Democratic efforts are segmented in the overlapping efforts of various campaigns and state parties and unions.

Harold Ickes, a White House official in the Clinton administration, has sought to remedy that with a private firm, Catalist, which is refining a national voter database drawing from and providing a resource for various Democratic and left-leaning groups. The AFL-CIO is one of Catalist's clients.

Pennsylvania's 4th Congressional District is one laboratory for a contest between the Republican's tested machine and the Democrat's less monolithic approach. Both sides are working the district with door-knocking, mailings and phone calls. The district has a heavy labor presence.

"[USW President] Leo Gerard was out in the rain, rallying the troops in Mercer," Mr. Rocha said, describing one part of an October weekend effort. Scores of automated calls went out from the USW building with the voices of either Mr. Gerard or a local labor leader.

The separate Democratic coordinated campaign wa sending teams walking that district and others across the state this weekend. Robocalls are going out with the voices of Democrats, including, former President Bill Clinton; U.S. Sen. Hillary Clinton, D-N.Y.; Robert P. Casey Jr.; and Mr. Rendell.

In the northern suburbs of Allegheny County that fall within the 4th District, Democrats will receive phone calls from county Chief Executive Dan Onorato touting the candidacy of Jason Altmire.

On Election Day, operatives from both parties will be scanning voter lists through the day, checking off those who have voted and preparing for a late-hours push to call, cajole and, if necessary, drive friendly voters to the polls.

Campaigning with Mr. Altmire last week, Howard Dean, the Democratic National Committee chairman, insisted that his partisans would not be out-organized by the GOP.

"I don't think they'll beat us on turnout, I really don't," he said. "Rendell has a terrific operation. We've been on the ground for a year and a half, so I think it's safe to say we have a much better turnout operation."

Mr. Rendell said a big part of the question of who actually shows up at the polls is beyond the control of even the sharpest and best-prepared operatives.

"You can't get people to turn out if they're not enthusiastic," he said as he courted voters during a walking tour of Springdale on a recent Saturday. "And I believe that Democratic voters and independent voters are more enthusiastic about this election than Republicans are," he said.