PORTAGE, Wis. — The attack ads began in early 2017, planting doubts well ahead of the 2018 midterm elections. Against ominous background music and storm clouds, the Republican-financed spots hit Tammy Baldwin, Wisconsin’s Democratic senator, over the Affordable Care Act, Iran and veterans’ health care.
By July, a Milwaukee radio station was carrying audacious ads about Ms. Baldwin’s support for abortion rights.
“Did you know one out of three babies aborted in America are black? One out of three. And Tammy Baldwin is a big reason why,” the ad said. “That could be the next Frederick Douglass or Rosa Parks or Martin Luther King they’re aborting.”
Then came the positive ads describing one of her opponents, Kevin Nicholson, as a former Marine; an “outsider”; a businessman; and, like Ronald Reagan, a convert to conservatism.
For many national Republicans, Ms. Baldwin has emerged as the top target in the 2018 midterms: Donors from outside the state are spending twice as much money on the race so far as on any other Senate contest this year, according to an analysis by the Center for Responsive Politics, a nonpartisan group that tracks money in politics. Much of the money has gone toward television and radio ads.
The big spending doesn’t just signal that each party sees the Senate seat as winnable. It’s also a measure of intensity on both sides to prevail in Wisconsin after Donald J. Trump shocked Democrats in 2016 by being the first Republican presidential nominee to carry the state since 1984. National Democrats are bent on winning it back in 2020 — and getting Ms. Baldwin re-elected is a crucial step toward that goal.
The fight may become the most expensive Wisconsin Senate race ever: An analysis by the state Democratic Party found that nearly $10 million in advertising had already aired or been purchased by outside groups against Ms. Baldwin or in favor of Mr. Nicholson. (Mr. Nicholson’s camp put the number at nearly $9 million.) At least another $3.7 million in advertising is underway sponsored by outside groups in favor of Ms. Baldwin.
The advertising by political action committees like Restoration PAC and Americas PAC — both heavily financed by the hard-right industrialist Richard Uihlein — has propelled the first-time candidacy of Mr. Nicholson, and underscores the influential role that outside conservative PACs play in this politically polarized state. Organizations funded by Mr. Uihlein and the billionaire Koch brothers have devoted millions to assuring continued Republican control of the Senate, and many conservatives view Ms. Baldwin, 56, as a beatable first-term senator who symbolizes the extreme left wing of the Democratic Party.
“Tammy Baldwin is very vulnerable,” said Brad Courtney, the state’s Republican chairman, calling her one of the Senate’s most liberal members. “There’s going to be lots of money coming into Wisconsin.”
Even in this rural area of small farms, nearly two hours from Milwaukee, it’s hard to avoid the drumbeat of ads, which began well before the traditional start of campaign season.
“I hear a lot of stuff on the radio,” said Gary Buchholz, a soil technician who was part of the crowd at J & J Fireball Lanes, a local bowling alley, and plans to vote for Ms. Baldwin. “I don’t like the money that comes in from out of state, huge amounts of money trying to influence Wisconsin elections.”
Partly to counter the advertising, an energized Democratic base is organizing early, determined to retain the Senate seat held by their party since 1957, when William Proxmire was elected to the unexpired term of Joseph McCarthy, who had died in office. Yet Wisconsin has become a Republican stronghold: The state not only voted for Mr. Trump, but has also become a laboratory for conservative policy ideas under its two-term governor, Scott Walker, and the Republican-controlled legislature.
In November, Ms. Baldwin is expected to face either Mr. Nicholson or Leah Vukmir, a conservative state senator favored by the state’s Republican establishment….
