If Rep. Tammy Baldwin (D) ekes out a win in the Wisconsin Senate race, it might be because she closely copied the successful media strategy of the state’s conservative rock star,  Gov. Scott Walker.

Baldwin built a huge media advantage last month, spending millions of dollars on attack ads to knock down former Gov. Tommy Thompson (R), much to the consternation and befuddlement of Badger State Republicans. Now, with both the Senate and presidential races tightening, Thompson finds himself fighting to find enough time and airspace to catch up.

Earlier this year, Walker and Republicans defined the gubernatorial recall election by getting out in front of the media barrage from outside groups. And though the stakes here are different, swaying overwhelmed Wisconsin voters early might prove a deciding factor in a race that could represent a key pickup opportunity for the Senate GOP.

With just three weeks until Election Day, any attempt by Thompson to match Baldwin’s air power could be muddied by the new influx of money from GOP presidential nominee Mitt Romney and outside groups seeking to swing the state his way.

“If all of these groups rush in to try to get Romney across the finish line, how does that affect Thompson? There are certain groups that are backing [Thompson], but it’s going to clutter the market, dilute their message and make it more expensive,” said one GOP operative unaffiliated with either campaign. “The costs for the [National Republican Senatorial Committee] or Crossroads — or even the Democratic Senate committee for that matter — it’s going to make it more expensive for them to deliver a message in the end.”

The operative pointed to the strategy used by Walker and the Republican Governors Association earlier this year as “a pretty good dry run for how to win the state,” noting that by the end of the race, the election had become so heated and partisan that few undecided voters remained. 

“Walker and the RGA had controlled the message early just by sheer force,” the source said.

Of course, the GOP’s get-out-the-vote machine was another key to Walker’s landslide win, and Republican sources say their established ground game will work toward Thompson’s and Romney’s advantage.

Still, between Labor Day and this week, Baldwin’s campaign spent 2.5 times as much as Thompson’s did on media, resulting in a nearly 3-to-1 advantage in ads on the airwaves and a boost for the Madison Democrat in the polls. Since then, the race has narrowed significantly, and Democratic and Republican sources in Wisconsin and Washington, D.C., say the performance of President Barack Obama and Romney at the top of the ticket is still the Senate race’s most important factor.

But like most tossup Senate contests across the country, Wisconsin’s race has been defined by negative ads, which could make the election a choice of which candidate voters dislike less. 

A Marquette University Law School poll released Wednesday showed Baldwin trailing Thompson by 1 point, after leading him by 9 points four weeks ago. Obama also saw his lead shrink to 1 point, after being up 11 points two weeks ago. 

Thompson, who emerged from a bruising, four-way August primary, had been cash-strapped and unable to go on the air in the days after he won. 

His most recent unfavorable ratings in the Marquette poll have remained constant at 49 percent or 50 percent — a media battle scar that runs deep. Baldwin’s unfavorables, however, rose 7 points to
47 percent over two weeks, after Thompson and the NRSC started running ads against her. 

A source tracking Romney’s operation in Wisconsin noted that the campaign is now “flooding the zone” in the Badger State, which could make it more difficult for the Senate ads to break through. 

Given the high cost of getting into the media game, much of the onus will fall on outside groups, especially in the case of Thompson. 

The Thompson campaign had not, as of Tuesday, made ad buys for the campaign’s last two weeks, according to a document obtained by Roll Call from a GOP source. Baldwin’s campaign was tentatively slated to spend $1.1 million on radio and TV ads over that same period.

Moreover, Thompson’s campaign trails Baldwin’s by $1.4 million in cash on hand.

In the days ahead, Republican outside groups are expected to step up their game and hope to make Baldwin even less popular with voters. The NRSC is scheduled to spend $2.9 million in the campaign’s last three weeks, and American Crossroads is slated to chip in almost $3 million, in addition to about $5 million Crossroads GPS has already spent on the race. The Democratic Senatorial Campaign Committee is slated to spend about $2.6 million in the final three weeks on Baldwin’s behalf.

“The reality is, you just hit a saturation point in any of these races where the messages have to become more creative and the topics have to change to make them more effective,” said a Republican operative affiliated with a group supporting Thompson. “She’s not as well-known as him, so there’s still room to grow that message in a way that also feeds into the narrative of the recall — no one wants to elect someone who’s too extreme, who is going to embarrass them.”

Even with all of the negative ads, sources say, it’s still on the candidates to run good races, avoid major gaffes — like Thompson’s son saying at a closed-door fundraiser that Obama should be sent “back to Kenya” — and make their final pitches to voters. 

Baldwin and Thompson are set to have their second of three debates tonight in Wausau.

“The only person who can close the argument is the candidate. Outside groups can’t,” the outside group operative said. “We can boost negatives against an opponent, but we can’t close the deal.”