HUDSON, WIS. - Across the St. Croix River on the western edge of Wisconsin, a long-brewing political storm will touch down Tuesday. There -- and in several other state Senate districts -- voters will cast ballots in extraordinarily heated political races that have huge implications for Wisconsin's political future.

The bitter winter protests over Gov. Scott Walker's new collective bargaining limitations on state workers, which gripped the nation, have given way to unprecedented recall elections for nine state senators. The results will determine whether Republicans retain control of the Wisconsin Senate. But they also may offer a glimpse into broader voter sentiment heading into the coast-to-coast elections in 2012.

"I think this is going to send a message throughout the country," said Bruce Faribault, a St. Paul resident standing alongside the UFO Days Parade in Elmwood, Wis., one recent afternoon to support Democrat Shelly Moore.

The recall races are attracting outsized national attention for state legislative elections.

In the typically placid district encompassing Hudson and River Falls, roughly $5 million has been spent in the battle between Republican incumbent Sen. Sheila Harsdorf and Moore, a local teacher and union activist. Almost all of the money has come from outside groups.

Streets are lined with lawn signs, houses are flooded with campaign mailers and the political conversation frequently spills into local businesses like City Barbershop in Hudson. "Most of them are upset about the recall and the election," owner Ann O'Brien said of her customers who support Harsdorf.

O'Brien's 21-year-old son, Mac Spohn, sees it differently. "She was recalled for a reason," Spohn said of Harsdorf, noting her support for cuts to his technical college.

Recall supporters gathered more than 23,000 signatures this spring to trigger the election. Moore then cleared a primary election against a Republican running as a Democrat, one of a number of so-called "fake Democrats." Moore won by 10 percentage points.

Polling in the race has been limited, but a recent Democratic poll showed Moore trailing Harsdorf by three points. Harsdorf has raised more than $430,000 -- four times her 2008 war chest -- while Moore has taken in $335,000. The campaigns are focused intently on voter turnout, which could be the most unpredictable and important factor in a summer off-year election.

"There's more activity in this state Senate race than we saw in presidential races in my neighborhood," said Mike Zipko, a Twin Cities media and political consultant who lives in Ellsworth, Wis. Zipko recently hosted a fundraiser for Harsdorf in St. Paul.

The collective bargaining changes that first sparked the recalls have since taken a backseat to more familiar debates over taxes and spending that also have been saturating politics at the Minnesota Capitol and in Washington. A recent debate in River Falls touched on collective bargaining but pivoted to job creation and fiscal issues. Moore homed in on fresh cuts to government services, while Harsdorf warned that higher taxes would drive jobs out of Wisconsin.

Moore says the race reflects voter frustration with a legislative process at the Capitol in Madison that ignored their input and featured late-night votes.

"They [voters] feel like they've lost democracy," Moore said while greeting volunteers at her campaign office in River Falls. "So this is them taking that back."

That's the sentiment of Krista Spieler, a Moore supporter who was at the office. "It really felt like from the beginning the door was shut and there wasn't space for dialogue," Spieler said.

Harsdorf contends that collective bargaining remains the primary fuel behind her opponents' efforts. "They might want to talk about other issues," Harsdorf said. "But the reality is ... that's been driving this from the very beginning."

For some voters, the union issue is still a primary concern. "She is all for the union," Elmwood resident Dee Nazer said at the UFO Days Parade, referring to Moore. "The union's not for the people; they're for themselves."

Outside money

Political observers are aghast at the amount of money that outside groups have shoveled into the recall elections.

Mike McCabe, who heads the Wisconsin Democracy Campaign, a watchdog group, estimates that total interest group spending across the state on a cluster of legislative seats has reached $26 million, an amount more typical of a U.S. Senate race. Only $13.2 million of that came from groups that publicly report their donors.

Outside groups have bought nine TV ads in the Harsdorf race. Harsdorf has bought only one. Moore has no TV ads running. To reach Wisconsin voters on the border, television ads have been bought in the pricier Twin Cities market, where ad spending has surpassed $1.5 million, said Ken Goldstein, president of Virginia-based Kantar Media CMAG, which tracks political advertising. Goldstein said major political groups likely see the races as valuable testing grounds for future elections.

"It's sort of become a proxy for a more general battle that's going on between Democrats and Republicans nationally," he said. "And what's going to go on into 2012."

Two fiscally conservative groups, Wisconsin Club for Growth and Citizens for a Strong America, have aired ads highlighting Moore's union history. "We breathe union," Moore tells a crowd of protesters in Madison. Neither group returned calls for comment, and both list a UPS store as their primary address.

Wisconsin Club for Growth's IRS filing lists a $250,000 contribution from Chief Oil & Gas CEO Trevor Rees-Jones and another $150,000 from Citadel, a financial services firm in Illinois. Citizens for a Stronger America does not report its donors.

The union-backed We Are Wisconsin PAC, which does disclose its donors, has run a series of ads saying Harsdorf has "changed" and supports tax breaks for the wealthy. We Are Wisconsin has raised millions largely by tapping national labor unions.

It's a lot of money to reach undecided voters in a tiny sliver of the Twin Cities market. "They're using a shotgun to do a rifle's job," McCabe said.

Final push

Six Republican senators face recall elections Tuesday. On Aug. 16, voters will decide on two Democratic senators. One Democrat already won his recall election in July.

The final days of the race will bring even more outside help -- this time from Minnesota. The Minnesota Republican Party is sending volunteers to Hudson for phone bank work and literature drops to counter "the union bosses." The Minnesota AFL-CIO also plans to do phone bank work and to drive volunteers in for canvassing.

If Democrats win enough races, they are expected to set their sites on a recall of Gov. Scott Walker next year. Democratic Sen. Mark Miller, one of the senators who fled to Illinois this winter in an attempt to block Walker's budget, said a "strong victory" on Tuesday would create the impetus for a Walker recall.

Eric Roper • 651-222-1210 Twitter: @StribRoper