A multimillionaire who finances his own campaigns, Kohl shuns publicity while quietly working to protect the dairy industry, the elderly and farm programs.

Perhaps the most introverted member of the Senate, Kohl is known for thoughtful gestures, such as sending out boxes of Wisconsin chocolates, and providing breakfast in his office on Wednesdays for visiting constituents. But he’s not afraid to take a tough stance.

Order the 2012 Politics in America book.

Late in 2010, Kohl said he would place a hold on Michele Leonhart, the White House’s nominee to lead the Drug Enforcement Agency, because Kohl feels that DEA rules cause health care workers to needlessly deny painkillers to people living in nursing homes. Heightened scrutiny of prescribing practices has resulted in elderly people suffering in pain as nurses and doctors strive to adhere to the Controlled Substances Act, he said. He grilled Leonhart about this at a November hearing of the Judiciary Committee.

“When I met with you in early May, you assured me that this was a priority, and that you also would address the problem swiftly,” said Kohl, who is the No. 2 Democrat on Judiciary and chairman of the Special Committee on Aging. “It appears that DEA is putting paperwork before pain relief. I would like to see much more progress made on this issue before you are confirmed.”

After getting assurances from the Justice Department that the medication would be delivered to patients, Kohl released his hold.

As chairman of Judiciary’s Antitrust, Competition Policy and Consumer Rights Subcommittee, he has pushed legislation to stop makers of brand-name drugs from paying would-be competitors to delay the market entry of cheaper generic versions of their products. The bill might save the federal government as much as $2.6 billion over 10 years by reducing its drug costs.

“At this time of spiraling health care costs, we cannot turn a blind eye to these anti-competitive backroom deals that deny consumers access to affordable generic drugs,” Kohl said.

Kohl has worked with Republican Charles E. Grassley of Iowa on that effort, and also on nursing home legislation. Grassley told Milwaukee magazine that he’s accomplished more with Kohl while talking less to him than any other senator. “I’ll bet he never has done anything to harm or hurt anybody behind their back,” Grassley said in the magazine’s 2010 profile of Kohl.

As chairman of the Appropriations Subcommittee on Agriculture, Kohl has pressed for accountability while looking out for Wisconsin’s economic mainstay — farming. In the 110th Congress (2007-08), he included in the law to reauthorize farm programs a provision to permit interstate sales of state-inspected meat products, which he says will help smaller entrepreneurs expand their markets.

Kohl joined the Banking, Housing and Urban Affairs Committee in the 110th Congress. The financial services overhaul enacted in 2010 makes regulators responsible for decisions on issues ranging from determining fair charges on debit card swipe fees to deciding when a risky firm should be taken over, and Kohl pledged to make sure the American public gets the intended benefits. “I am going to keep a watchful eye on the regulators to make sure they are given adequate resources and oversight to do the job that they have been charged with,” Kohl said on the Senate floor in 2010.

Kohl is typically a loyal party vote. Yet he considers himself a moderate who sees partisanship as the biggest obstacle to legislating, so at times he steps across the aisle to further his goals. He joined in 2007 with New Mexico Republican Pete V. Domenici on a bill calling for a nationwide system of background checks to identify job applicants who have criminal pasts.

In 2001, he was one of a dozen Democrats to vote for President George W. Bush’s $1.35 trillion tax cut, and one of 15 Democrats to back the initial version of the GOP’s spending blueprint for the year. However, he opposed Bush’s 2003 plan for $350 billion in tax cuts over 11 years. He voted for a two-year extension in late 2010.

With Republicans narrowing the gap in the Senate and taking control of the House in the 112th Congress (2011-12), Kohl’s interest in reining in the federal deficit might be revived, though he expressed no support for the spending proposal put forth by fellow Wisconsite Paul D. Ryan, the Republican chairman of the House Budget Committee. His preoccupation with the deficit echoed that of his predecessor in the Senate, Democrat William Proxmire, renowned for his sermons against government excess.

Kohl was among the 53 senators who voted in January 2010 in support of a bid by Budget Chairman Kent Conrad, a North Dakota Democrat, and Judd Gregg of New Hampshire, the committee’s ranking Republican, to establish a powerful commission to tackle the federal debt. The effort failed — 60 votes were needed — but it paved the way for President Obama’s fiscal commission, which in December made a set of sweeping recommendations on the budget.

Even though Kohl said he would not endorse the commission’s entire plan, particularly changes to Social Security, he praised the effort and called it “an important step to getting our fiscal house in order.”

Kohl, one of the wealthiest members of Congress, considers himself something of a bargain for the taxpayer. Though he has to receive the pay increases given to Members of Congress, at the end of each year he writes a check to the Bureau of Public Debt for the difference between his salary (currently $174,000) and the $89,500 he earned upon joining the Senate. He also has returned more than $5 million in unspent office allocations.

Kohl’s parents immigrated to the United States in the 1920s — his mother from Russia, his father from Poland. They opened a small food store on Milwaukee’s south side, where Kohl worked after school and on weekends. One of his childhood friends (and later his college roommate) was Bud Selig, who went on to become a successful car dealer, owner of the Milwaukee Brewers baseball team and commissioner of Major League Baseball.

After earning a master’s degree in business from Harvard, Kohl returned home and, with his two brothers, set about expanding the family grocery business into a department store chain in 1962 — the same year that Sam Walton opened the first Wal-Mart Discount City store in Arkansas. The Kohls eventually owned hundreds of stores before selling the chain in 1979.

In 1985, Kohl bought the Milwaukee Bucks NBA franchise, primarily to keep the team from relocating. He was a fan, and he saw the deal as “a combination of my own personal interest and public need.”

Kohl’s first public involvement in politics came in 1975 when Democratic Gov. Patrick Lucey asked him to chair the state Democratic Party. He did the job for two years, despite his discomfort with some of its public aspects. In 1988, when Proxmire stepped down after 31 years in the Senate, Democrats pressed an initially ambivalent Kohl to run. He had plenty of name recognition, and spent nearly $7.5 million (most of it his own money) on the campaign. Kohl’s total outlay was double the previous state record.

He won a three-way Democratic primary with 47 percent of the vote, and defeated GOP state Sen. Susan Engeleiter by 4 percentage points in the fall. Kohl has won with comfortable margins each time since, and his slogan in each campaign is the same: “Nobody’s senator but yours.” (This was also a theme used by Massachusetts Republican Scott P. Brown during his successful 2010 Senate bid.)

This profile appears in the 2012 Politics in America book and on CQ.com.