The days when Minnesota was nothing but a presidential campaign backwater are long gone.

Proof of that was abundant Saturday: two major candidates roared into the state in the waning hours before the biggest presidential primary day in American history.

Voters in 24 states will pick their candidates Tuesday, in what has become the first-ever national primary. Minnesotans who attend the DFL and Republican precinct caucuses will find themselves smack in the middle of things.

Saturday's biggest appearance came in the afternoon, when thousands of people jammed Target Center to see Democrat Barack Obama. A few hours later, Republican Mitt Romney appeared before a more modest gathering in Edina. And Hillary Rodham Clinton was headed for the Twin Cities today.

Party leaders believe that state residents will seize the opportunity created by this new presidential competitiveness in near-record numbers.

"We've been doing TV, radio, mailings all over the state," said state Republican chairman Ron Carey. "We're pushing harder than we ever have before, so we think we're going to get the turnout."

Added Brian Melendez, his DFL counterpart: "The phone's ringing off the hook all day long, the website's getting 1,000 hits a day. If we don't break the record, it'll be close."

For the DFL, that would mean exceeding the turnout of 75,000 in 1968, when favorite sons Hubert Humphrey and Eugene McCarthy were among those fighting for the nomination. For the GOP, it would mean turning out more than the 30,000 who showed up in 1996.

Different stakes

Historically, the DFL has poured more energy and bodies into the caucuses than the Republicans. A turnout gap this year could owe something to a basic structural difference in the parties' presidential preference ballots.

In brief, the DFL results Tuesday will matter far more than the Republicans' will.

On the Democratic side, 72 delegates will be pledged to a candidate, a binding result at this summer's national convention.

On the GOP side, the caucus vote is essentially a beauty contest with no delegates directly at stake, giving the winner bragging rights when, in Carey's words, "the national media report that Minnesota goes for candidate X."

Romney's visit notwithstanding, there's been scant visible activity on the Republican side, with skeletal staffing and no advertising. Only Ron Paul, who remains a long shot, has opened a fully staffed office in the state. He plans to hold a rally at the University of Minnesota on Monday night.

By contrast, Obama's and Clinton's campaigns have for months had multiple field offices, paid staff members, phone banks, mass mailings, caucus training sessions and door-knocking campaigns. Obama also has made a substantial ad buy in the state.

Polls give little insight

Predicting the GOP and DFL winners Tuesday night is nearly impossible. What little polling has been conducted provides only a hint of the possible outcomes.

A poll released last week by Minnesota Public Radio and the University of Minnesota's Humphrey Institute showed John McCain with a commanding lead among Minnesota Republicans. Former Arkansas Gov. Mike Huckabee was a surprisingly strong second, apparently thanks to his under-the-radar outreach to evangelical Christians. Romney was running third.

But the poll, like previous ones, reflects the preferences of all DFLers and Republicans in the state -- not the small number who actually show up to caucus.

In the Democratic race, the poll showed Clinton with a slight lead, within the margin of error, over Obama.

One potential measure of support among political insiders in Minnesota can be gleaned from the candidates' fundraising success. Obama and Clinton each raised more than $600,000 from Minnesotans in 2007, trading small leads all year and ending with Clinton just $23,000 ahead.

Yet another indirect measure of support in the contest that will award convention delegates Tuesday are the DFL's 14 "superdelegates," party big shots who are formally uncommitted to a candidate, but who could be influential or in a position to anoint the ultimate nominee if neither Obama nor Clinton can nail down a majority of the pledged delegates.

The superdelegates -- members of the party's congressional delegation and a handful of party activists -- have sent somewhat different messages.

Of those who have committed to a candidate, four -- with former Vice President Walter Mondale at their lead -- are backing Clinton. Three members of the congressional delegation -- Keith Ellison, Betty McCollum and Jim Oberstar -- support Obama.

In Minnesota and other Super Tuesday states, the Obama and Clinton campaigns have been avidly courting supporters of Sen. John Edwards, who has quit the race.

The Edwards voting bloc is seen by both campaigns as crucial to securing a majority of delegate votes at the national convention Aug. 25-28 in Denver.

The passion of Edwards' supporters was clear at his final campaign appearance in St. Paul on Tuesday, when more than 1,000 full-throated union members turned out on a bitterly cold night.

Oberstar, representing the most deeply Democratic district in the state, said he thinks those union members, the core of Edwards' support, are likely to embrace Obama.

"I think Senator Obama is going to resonate very strongly with a large majority of Edwards advocates," he said. "You'll see very strong support on the Range, in Duluth, along the North Shore."

Bob von Sternberg • 612-673-7184