The next big date on the electoral calendar isn't in November, it's next week.

On June 5, Republican Gov. Scott Walker faces off against Democratic challenger Tom Barrett in a recall election. The race has received a great deal of attention both inside and outside the state, and spending has topped $60 million, according to figures from the nonpartisan Wisconsin Democracy Campaign.

Almost half of the $62 million spent so far has come from Walker. Campaign finance reports show that the embattled governor has spent $29 million on the race. Democratic candidates have spent around $4 million, with Barrett accounting for about $2.9 million of that total. The remaining money has come from outside spending groups, about $21.5 million from the groups that have reported their spending.

The Wisconsin Democracy campaign estimated that an additional $7.5 million has been spent by "issue ad" groups, but that figure is likely a conservative estimate, said the group's executive director Mike McCabe.

"There's no public record that can be used to estimate or quantify what these groups spend," McCabe told ABC News. "It's really hard to put a price tag on direct mail that's being sent out. We don't have good sources of data on Internet advertising, even radio is hard to track. So they're clearly conservative numbers, but they're based on known activity, particularly television advertising."

Some of the issue groups identified as participating in the recall include Americans for Prosperity, the Republican affiliated organization founded by the billionaire Koch brothers, and the Greater Wisconsin Political Fund, a 527 arm of the Democratically affiliated group Greater Wisconsin.

The $60 million may pale when compared to the reported $1 billion spending plans of Republican-affiliated outside groups in the lead up to the election in November, but for a single statewide race it's an extremely high figure. Spending in the Republican Senate primary in Texas, for example, the most expensive Senate race in the country, totaled $25.5 million before this week's primary.

Walker, 44, has also led the Democrats raising money. The governor has raised $30.5 million since January 2011, the vast majority of which came in since the recall efforts began in November.

Barrett, 58, has raised $3.9 million since entering the race in March, but a larger percentage of his donations have come from in-state. Seventy-four percent of Barrett's individual donations have come from Wisconsin residents, while 38 percent of Walker's individual donations have come from in-state.

The large percentage of money coming from out of state is unprecedented for Wisconsin, says McCabe.

"Obviously, one thing that's really striking here is just the sheer volume of money that's being spent, but the other thing that's really striking is how much money is coming from out of state," McCabe said. "We've never seen this much outside interference. Most of the money that's been spent in this race has been spent by people who can't vote in the election. That's unprecedented for this state."

Powerful surrogates have gone to Wisconsin to campaign for both candidates. Govs. Chris Christie of New Jersey and Bobby Jindal of Louisiana have campaigned for Walker, and today reports emerged that Bill Clinton will travel to Wisconsin to campaign for Barrett.

Recent polling shows Walker with a lead over Barrett. A poll released on Wednesday from Marquette University Law School showed Walker with a 7 point lead heading into the final slog of the campaign, outside of the polls margin of error of 4.1 percent. Walker had 52 percent to Barrett's 45 percent.

For all the money that's been spent, the polling numbers have been fairly consistent, said McCabe.

"So far, the tens of millions of dollars that have been spent on ads don't seem to have moved the needle very much," McCabe said. "Poll numbers haven't changed much. Walker's approval ratings haven't changed. So the tens of millions spent don't seem to have changed very many minds.

"I don't think the ads are as effective in this election as they normally are. I actually think a lot of this money will be wasted. I think the election will really come down to who gets out the vote, I think it really will be decided by a ground gain, not the air wars."

Democrats and Republicans in the state are likely to agree with that assessment. Officials for both state parties maintain that the election will be driven by turnout, and both parties claim large ground operations.

This is, at least to some degree, because polling has shown Walker to be a polarizing figure. It doesn't appear as though there are many undecided in the race.

"I think that in this election, you have very few undecided voters, people either love Scott Walker or they hate Scott Walker with a passion. There's not much in between with the guy. … I think this is an unusual election because there just aren't many undecideds here" said McCabe.