The Twitters bring word that former Maryland Governor Martin O’Malley is likely to announce on May 30th that he’s entering the Democratic presidential primary. As John Wagner puts it, all signs are that O’Malley will position himself as “a more progressive, forward-looking alternative” to Hillary Clinton.

With Senator Bernie Sanders already running, we now have something of a debate taking shape. Even if Clinton’s ultimate victory seems all but assured, she could face tough questions from the left on a range of issues. Here’s a partial rundown:

Trade: All signs are that Clinton is waiting to see whether Fast Track is defeated in Congress, which would relieve her of the need to take a position on it. But yesterday’s events in the Senate suggest it is anything but dead. Clinton has suggested the Trans-Pacific Partnership must “raise wages and create more good jobs at home.” But the hard part will come in the debate over whether the eventual TPP does that, meaning Clinton has left the door open to either supporting or opposing the deal, which Sanders and O’Malley both oppose.

Nor has Clinton said anything about the Fast Track process, which itself is controversial among Democrats. This could pass Congress and be heading to the president’s desk very soon. What will Clinton say about it?

Wall Street: There are two poles that define the economic debate among Democrats. There’s the mainstream Dem agenda that focuses on boosting wages and economic mobility and opportunity through family-friendly workplace flexibility policies and more investments in education, job training and infrastructure. Then there’s the agenda embraced by Elizabeth Warren and Joseph Stiglitz, which is focused more on reforming rigged financial rules and deep structural problems that have exacerbated inequality, via a financial transactions tax, breaking up the big banks, much tougher Wall Street regulation and enforcement, and more.

There is a lot of overlap between those two agendas. But Sanders and O’Malley have more directly embraced the latter than Clinton has. As Jim Tankersly explains, while many Clinton advisers have embraced some of those latter ideas, she “has not come close to laying out a unified theory of the economy” that is premised on the latter approach’s diagnosis of our economic challenges. There is plainly a larger philosophical argument here that remains unresolved.

Iran: Clinton put out a statement calling the recently-announced framework an “important step” forward and expressing strong support for diplomacy as the best way to prevent Iran from gaining a nuclear weapon. But what happens if the specifics of an eventual Iran deal cause some hawkish and “pro-Israel” Democrats to balk? I expect Clinton to endorse the deal, if there is one, but Democrats and liberal activists wary of her hawkish streak — and vote for the Iraq War — will likely be looking to spotlight any signs of hedging.

Climate: Clinton has vowed to protect Obama’s actions on climate, which include far-reaching but not-yet-implemented rules curbing carbon emissions in existing power-plants and (hopefully) a global climate deal negotiated later this year. But Sanders has gone further, calling for a carbon tax and substantial investments in rail to “break our dependency on automobiles.” As Ben Adler has noted, Clinton isn’t a full blown “climate hawk,” and she may be overly pessimistic about the politics of climate change. It’s hard to imagine her embracing a carbon tax, though she now may find herself asked about it.

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* BATTLE LOOMS IN HOUSE OVER FAST TRACK: Today the Senate is likely to vote to move forward with the Fast Track authority that Obama seeks for negotiating trade deals, but the Post games out what looks like an even bigger challenge: getting it passed in the House. The key nugget:

Speaker John Boehner has warned that he could need more than 50 Democrats to support the bill. Obama has so far appeared to win firm or tentative commitments from fewer than half that many.

Will a large bloc of conservative House Republicans really vote against trade? There are signs the expected Tea Party rebellion is fizzling. Can Obama win over just enough Dems to cover the difference? Given the depth of anger over Fast Track among liberals, it may be tough.

* PRESSURE MOUNTS ON SENATE GOP OVER NSA SURVEILLANCE: The Post notes that the overwhelming House vote in favor of the U.S.A. Freedom Act, which would end much NSA bulk surveillance, will now put pressure on Mitch McConnell. The GOP Senate leader is still insisting he will push for a clean extension of bulk surveillance through 2020.

With bipartisan opposition mounting, the question now is how he will get from there to allowing a vote on some version of the House bill. Remember, the alternative is to let the relevant section of the Patriot Act expire entirely, and of course we can’t have that.

* FLORIDA MEDICAID FIGHT COMES TO DC: The Hill reports that House Republicans are set to hold hearings on the Obama administration’s treatment of Florida Governor Rick Scott’s administration. The focus is on the question of whether the refusal to reauthorize the hospital funding Scott wants amounts to an effort to coerce him to accept the Medicaid expansion.

Apparently it is “coercion” if the administration does not give in to Scott’s demand for federal funding for health care on the grounds that it not be part of “Obamacare.”

* THE LATEST ON THE AMTRAK CRASH: The train was traveling at 106 miles per hour, on a curve that is supposed to be approached at 50 miles per hour, but the key question right now is why:

There is technology available, known as Positive Train Control, that prohibits trains from exceeding speed limits. The system is in place in much of the Northeast Corridor, but Amtrak had not installed it on the section of track where the derailment happened. Congress has mandated that the system be installed throughout the U.S. rail system by the end of this year.

It will be interesting to see how this impacts the debate over Amtrak funding.

* THE AMTRAK CRASH AND THE NATION’S INFRASTRUCTURE: David Leonhardt reports that the crash in Philadelphia is already renewing the debate over whether we need to spend more infrastructure. Even if the crash was caused by the high speed, he argues, one reason trains can’t travel so fast (as in other countries) is that our rail system is ailing.

The key stat: Combined federal, state and local spending on construction “now represents about 1.5 percent of total economic activity, down from about 1.8 percent on average from 1993 through 2008. It’s at its lowest level in at least 22 years.”

* HILLARY RETURNS TO IOWA: Radio Iowa reports that Hillary Clinton is set to return to Iowa next Monday and Tuesday, and her “events will be similar to her stops in Iowa last month — small venues and small crowds.” Polling has shown Clinton with around 60 percent among Iowa Democratic caucus-goers, but no doubt memories of the 2008 Iowa caucuses still persist: hence the early attention to the state.

* AND ‘CLINTON CASH’ AUTHOR MAKES CORRECTIONS: Politico reports that Peter Schweizer, the author of “Clinton Cash,” has now corrected at least seven or eight inaccurate passages for a new edition of the book, after an aggressive push from the Clinton campaign to highlight the book’s flaws. Surely this will get as much attention as the original pre-publication promise of revelations did.