Newsletter: Essential Politics: Will Wisconsin be Donald Trump’s Waterloo?

If Donald Trump fails in his quest for the Republican nomination, future historians may look back at next week’s Wisconsin primary as the turning point.

For months, Trump has dominated the Republican field, but as Michael Finnegan and I described Thursday, the blustery New York businessman has suffered one of the worst weeks of his campaign in the run-up to the Wisconsin balloting. Polls in the state show him losing to Texas Sen. Ted Cruz by 10 points.

Good afternoon, I’m David Lauter, Washington bureau chief. Welcome to the Friday edition of our Essential Politics newsletter, in which we look at the events of the week in the presidential campaign and highlight some particularly insightful stories.

It’s not that Wisconsin was ever a slam-dunk for Trump — the state has a very conservative Republican electorate, which was bound to give significant support to Cruz. But a double-digit loss for Trump there, if that polling forecast holds up, would be a serious defeat.

Moreover, the state GOP’s “winner-take-most” rules mean that Cruz might be able to sweep the lion’s share, or perhaps all, of Wisconsin’s 42 Republican convention delegates. That would leave Trump needing to win about 6 in 10 of the remaining delegates in order to gain a first-ballot majority at the nominating convention in July.

Trump still could do that, starting with a big win in New York on April 19, but it would require winning California by a significant margin. For a look at where the California campaign among the Republicans stands now, check out our latest USC Dornsife/Los Angeles Times poll of California voters.

And here’s the link for full coverage of all the results of our poll — the Democratic race, the Senate contest and Californians’ views of trade, economic inequality and immigration.

Over on the Democratic side, Wisconsin likely will mean another win for Sen. Bernie Sanders, which will fuel the hopes of his supporters.

But the more significant test for Sanders and Hillary Clinton will come in New York, where many more delegates are at stake. Sanders is making a spirited effort there, as Evan Halper wrote. Actually winning the state would be a long shot for Sanders — despite his three-state win last weekend — but if he can do it, he would deliver a severe setback to Clinton.

Halper also took a look at the debate over whether Clinton has moved to the left during the primary campaign. The evidence suggests that voters don’t perceive a shift. If anything, Clinton appears more moderate to voters now than she did earlier.

On Tuesday, you can follow the outcome of Wisconsin’s voting as we post live results, speeches and analysis on Trail Guide.

And as the race unfolds, keep watch on the delegates in both parties with our Delegate Tracker, which shows where each candidate stands and where each has won support.

Meantime, as the race continues, we’re taking several different looks at the electorate. Check out David Horsey’s terrific illustrated visit to Trump Nation.

Or, if you prefer a data-oriented view, the Pew Research Center has just published a major new polling study of American voters that provides a lot of insight into our divided electorate.

Here are a few highlights:

— Trump supporters stand out from the rest of the electorate by their negative perceptions of the state of the country. Nearly half of Trump supporters, 48%, say economic conditions are poor, compared with fewer than one-third of Republicans who back either Cruz or Ohio Gov. John Kasich. On the Democratic side, only about 1 in 4 Sanders supporters and 1 in 6 Clinton supporters call the economy poor.

— Trump supporters also are especially negative about international trade, which is no surprise given the candidate’s position on the issue. About two-thirds of Trump voters say free trade agreements have been a bad thing for the U.S. Supporters of Cruz and Kasich are fairly evenly split on whether trade agreements have been good or bad for the country.

By 58%-31%, more Clinton supporters say free trade agreements have been good for the country than bad. The split among Sanders backers is surprisingly similar to that of Clinton supporters on the issue: 55%-38%.

— One issue on which Sanders supporters stand out from the rest of the electorate is on whether the U.S. has a positive impact on the rest of the world. Some 60% of voters say problems in the world would be even worse without U.S. involvement. Backers of Clinton and the three Republican candidates are all fairly similar on that subject.

By contrast, Sanders supporters divide fairly evenly. Roughly as many who say U.S. efforts to solve world problems usually end up making things worse, 45%, say those problems would be even worse without U.S. involvement, 49%.

— Cruz supporters stand out by their strong opposition to same-sex marriage and abortion. Almost three-quarters of Cruz voters say abortion should be illegal in all or most cases, compared with about half of Trump or Kasich backers and fewer than 1 in 4 of either Clinton or Sanders backers. Similarly, 70% of Cruz voters, but only half of Trump voters, one-third of Kasich voters, one-quarter of Clinton voters and one-sixth of Sanders voters oppose same-sex marriage.

— Finally, Democrats overwhelmingly say that the growing diversity of the U.S. has made the country a better place to live, with roughly three-quarters of both Clinton and Sanders voters agreeing on that point. Republicans are much more divided. Slightly more than half of Kasich voters, slightly less than half of Cruz voters and only 4 in 10 Trump voters say diversity has made the U.S. better.

One other key polling number: Trump has become the most unpopular major political figure in decades. Overcoming that unpopularity would be a huge hurdle if he becomes the Republican nominee.

A few other stories that are well worth a read:

As Chris Megerian described, Kasich is trying to convince everyone that he’s more than just a one-state wonder. The Ohio governor cannot win enough delegates to gain a first-ballot majority at the convention but hopes that a contested convention might turn to him as the most electable of the GOP hopefuls in November.

Cathy Decker took a look at the controversy over Trump’s statements on abortion.

Lisa Mascaro looked at how the honeymoon may be over for House Speaker Paul Ryan.

Seema Mehta broke down a new California-based anti-Trump PAC’s plan to stop him from winning the nomination at the state’s June 7 primary.

And Mike Memoli looked at the politics of the continuing fight over the Supreme Court nomination of Judge Merrick Garland. As Memoli explained, the White House strategy is to slowly erode Republican resistance to Obama’s pick, and officials believe they are making progress.

What we’re reading

Ron Brownstein, always one of the most insightful analysts of politics, took a look at how Trump’s efforts to reinforce his support among his core voters has the effect of alienating others, what he refers to as the Trump Treadmill.

And it’s no surprise that Mike Murphy, the former top strategist for Jeb Bush’s super PAC, doesn’t like Trump. But in this interview with the Washington Post, Murphy provided an excellent insider’s view of what a contested GOP convention might look like and why Trump is unlikely to win the nomination if he cannot claim it on the first ballot.

That wraps up this week. My colleague Christina Bellantoni will be back Monday with the weekday edition of Essential Politics. Until then, keep track of all the developments in the 2016 campaign with our Trail Guide at our politics page and on Twitter at @latimespolitics.

Send your comments, suggestions and news tips to politics@latimes.com.