Today’s special election in Arizona will decide the next occupant of what Democrats call “Gabby’s seat,” and party operatives on both sides agree there is no clear favorite heading into Election Day.

The battle between Democrat Ron Barber and Republican Jesse Kelly to replace former Rep. Gabrielle Giffords (D) has been tight from the beginning. But Democrats in particular have varied between moments of confidence and doubt over the past several weeks and appear to have more riding on a victory.

“There’s a real chance Democrats are going to lose the seat, and it’s a pretty troubling place for us to be in,” said an Arizona Democrat not working on the Barber campaign.

Giffords, who resigned to focus on recovering from an assassination attempt last year, came to Tucson over the weekend to support Barber and to thank volunteers. Democrats came out of the weekend encouraged by their efforts to excite voters.

But it may have come too late. Early voting participation has been high, and most operatives believe a majority of votes in the special were cast before the Giffords appearance.

The high return on early voting ballots has surprised many and thrown off turnout expectations.

“If you don’t have your act together on the day early ballots go out, you’re really in trouble,” said former Rep. Jim Kolbe (R), who held the seat prior to Giffords.

Strategists from both parties said they have closely watched early ballot returns and have cause for optimism.

A pre-election survey from Public Policy Polling, a Democratic firm, showed Barber ahead by 12 points. But insiders were dubious, and Democrats said the race is “considerably closer” in their internal polling.

Outside groups such as the Democratic-aligned House Majority PAC and conservative-backed FreedomWorks, as well as the House campaign committees, have poured more than $2 million into the race — much of it spent on television ads.

As of last week, the Democratic Congressional Campaign Committee had spent $460,000 on independent expenditures, compared with $878,000 on IEs spent by the National Republican Congressional Committee. House Majority PAC had spent $473,000 on IEs, while FreedomWorks had spent $300,000.

Much is at stake for both parties. Democrats continue to say they can retake the House this fall, and holding this seat is a crucial part of their math. A Kelly win, on the heels of Republican Gov. Scott Walker’s victory in last week’s Wisconsin recall elections, would further give the GOP a boost and a key talking point.

“I think it’ll be good momentum for Democrats nationally [if Barber wins], but if we can’t keep Gabby’s seat, I think the Republicans are going to have a field day with this,” said Mario E. Diaz, an Arizona Democratic consultant who is not working on the campaign. “It was just presumed we were going to win.”

The refrain among Arizona operatives is that the GOP has always had the advantage in this district but that Giffords was an exceptionally charismatic and adept politician who pulled out an especially difficult win in 2010. Her legacy both motivates and looms over the party as it tries to hold the seat, but not to the extent as was expected.

“This election turned out not to be a referendum on Gabby Giffords but on the two candidates running here,” Kolbe said. “There was a lot of feeling that that’s what it would be about, and it has not turned out that way.”

But those on the ground said much more is at play than a single nationalized issue like in the special election last year that brought Rep. Kathy Hochul (D-N.Y.) to Congress.

As in that race, Medicare and Social Security are prominent in television ads and campaign rhetoric, but other factors are equally at play. Giffords’ endorsement counts and will surely earn Barber some crossover votes from Republicans.

If Barber loses, some Democrats are sure to privately point fingers at the disorganized start to the race in the wake of Giffords’ surprise resignation announcement in January.

The winner of the special will run for re-election in the fall for a full two-year term. That election will be in a redrawn district that is slightly more favorable to Democrats. But party strategists would much rather be defending the seat than trying to unseat a Republican incumbent in November, regardless of the district’s political lean.

If today’s outcome is a surprise blowout, the parties have few options to look for a new candidate in the fall because the filing deadline for the August primaries has passed.

Barber and Kelly have stated an intent to run in the fall, but there are opponents in each race. If Kelly loses today, it is hard to imagine national Republicans investing so heavily in him as their candidate again in the fall. If Kelly wins, Democrats will make winning back the seat a top priority this fall.

Regardless, one party will be able to crow about a win Wednesday and strategists will try to spin national implications. But Arizona operatives said it will be hard to sell the outcome as a foreshadowing of what’s to come this fall.

“There are too many dynamics in this race for anyone to point to one thing and say, ‘That was it,’” the Arizona Democratic strategist not on the campaign said.