What's likely to be an acrimonious debate between Senate Democrats and President Obama is approaching over free trade. The latest news is that lawmakers will ask for any agreement to include a provision to stop foreign countries from manipulating their currencies at the expense of U.S. manufacturers. Since whether or not the United States can reach a trade deal with several Asian countries will have major consequences for economies on both sides of the Pacific, here's a look at just what the senators asking for.

What's in Wonkbook: 1) Currency and free trade 2) Gerson, Rampell, Bouie and Meyerson on Republicans and the middle class 3) Where vaccine deniers live, and more

Number of the day: €1.1 trillion. That's how much the European Central Bank is prepared to spend to salvage the continent's economy -- and the total could well be higher. Matt O'Brien in The Washington Post.

Lawmakers will insist on provisions against currency manipulation in any trade deal. "Michigan Senator Debbie Stabenow said she was working with colleagues from both parties on a possible standalone bill to stop currency cheats and also aimed to ensure that an ambitious Pacific trade pact includes strict currency rules." Krista Hughes for Reuters.

The language could derail negotiations. "The U.S. auto industry, likewise, has indicated that it will oppose the TPP unless the issue is effectively addressed, and it has politically important supporters in the labor unions and the steel industry. At the same time, however, many observers believe that a U.S. effort to raise currency concerns would torpedo the agreement." C. Fred Bergsten in Foreign Affairs. 1/18/15.

JARED BERNSTEIN: Stopping currency manipulation is crucial. Exporting countries buy up U.S. dollars "to raise the value of the dollar relative to their own currencies, thus subsidizing their exports and taxing their imports. In the United States, the result is persistent trade deficits that have been a drag on growth and jobs — better-than-average manufacturing jobs — for decades." The New York Times. 1/19/15.

MIREYA SOLIS: A currency clause would be unworkable and counterproductive. " When countries maintain fixed exchange rates below their market value, impose extensive controls on capital inflows, and directly intervene in the market to defend a target exchange rate, it is easier to sustain charges of currency manipulation. But beyond these textbook cases we enter a wide gray area. ... A currency clause in the TPP can do much harm and little good." The Hill. 7/4/13.

GERSON: Republicans have an agenda for the middle class, too. "The new ideas found in the State of the Union speech — increasing the child-care tax credit, providing additional help to make community college affordable, paid maternity leave — are anything but boldly progressive. They are middle-sized proposals addressed to middle-class needs. ... Republicans have a case to make for their own version of middle-class economics. And, for the first time in a long time, they seem to want to." The Washington Post.

RAMPELL: Likely G.O.P. presidential candidates are having a "Piketty moment." "Here's Mitt Romney, in a speech last week: 'Under President Obama, the rich have gotten richer, income inequality has gotten worse and there are more people in poverty than ever before.' Sound-bite highlights from his past presidential campaign, you may recall, included a reference to the '47 percent' who don't pay federal income taxes and a conclusion that 'my job is not to worry about those people.' Apparently his job description has changed." The Washington Post.

BOUIE: Finally, Republicans are rejoining the economic conversation. "For as odd as it is to hear Romney (of “47 percent” fame) disdain the plutocratic economy, it’s also a welcome change. After 15 years of bad economic news—from sluggish growth and wage stagnation to a world-historical recession—we are finally at a point of real progress. Now is the time to talk frankly about what we need to further our gains and ensure broad prosperity. And, sincere or not, it’s good that Republicans want to be part of that conversation." Slate.

MEYERSON: It's all just talk. "The GOP would be happy to increase workers’ incomes if it didn’t involve diminishing the ability of wealthy investors and CEOs to claim the lion’s share of Americans’ incomes for themselves. Alas, for the Republicans, that’s arithmetically impossible. Once the national discourse turns to economic inequality, Republicans, already averse to the claims of science, will also have to dismiss the validity of math." The Washington Post.

King Abdullah of Saudi Arabia has passed away. "The monarch, believed to be 90, was succeeded by his brother, Crown Prince Salman, according to state television. That put the region’s most important Sunni power and America’s closest Arab ally in the hands of a 79-year-old who is reportedly in poor health and suffering from dementia." Kevin Sullivan and Liz Sly in The Washington Post.

Democrats are also divided on climate change. "Senate Democrats hoped to embarrass Republicans this week by making them vote that climate change wasn't real. Instead, Democrats exposed the fact they are divided on how to respond to the threat of global warming." Clare Foran in National Journal.

People who refuse to vaccinate their children tend to live near each other, making outbreaks more likely. These communities include some of the wealthiest areas of Northern California. Jason Millman in The Washington Post.

Chart of the day: Last year was a frightening one in the field of infectious disease, with nearly 700 cases of measles. Christopher Ingraham in The Washington Post.

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