* Ron Brownstein has a terrific piece explaining why basic structural factors pretty much ensure that the only action we’re getting on climate change will come from the exercise of executive authority:

The Democrats’ problem is that they cannot build a big Senate majority without winning seats in states heavily dependent on coal, which would suffer the most from limits on carbon. Democrats now hold 21 of the Senate seats in the 19 states that rely on coal to produce a majority of their electricity….Theoretically, those Democratic votes could be replaced by Republican votes from states less reliant on coal. But Republicans face overwhelming ideological pressure to oppose action on climate change and even to reject the scientific consensus that it is occurring…

As a result, despite Republican howls of executive overreach, there’s an air of inevitability to Obama’s shift on climate, toward regulatory action centered on higher vehicle-fuel-economy standards and the upcoming EPA regulation of carbon emissions from power plants…Obama’s tilt toward regulation captures a larger change. Because the Democratic electoral coalition is growing demographically but remains excessively concentrated geographically, the party now is more likely to control the White House than Congress. In a reversal, that is transforming Democrats into a party favoring strong executive action to advance its goals — and Republicans into defenders of congressional prerogatives.

This will probably be the major political fight of the summer, with untold ramifications in the Senate races, and its outcome may tell us more about Obama’s legacy than anything else.

* Jonathan Chait with a quick and useful look at the basic outlines of the decision Obama faces here, which will require balancing ambitious policy goals with the ability to withstand legal challenge, whose outcome could “literally determine the fate of the world.”

* It looks like Obama is gearing up to act unilaterally on immigration, too. The New York Times has this preview:

At a minimum, officials said the Department of Homeland Security was likely to issue new guidelines for law enforcement agents to make it clear that immigrants who are part of a family settled in this country should not be priorities for deportation, especially if their family includes American citizens. Officials are also considering changes that would shield some people who have returned to the country illegally after being deported. Right now, those people are charged with a felony and ordered out of the country.

However, such changes would only impact tens of thousands of people, far short of what advocates are hoping for.

* But what if Obama has more latitude to act than he has acknowledged? Also from the Times story:

Legal scholars say the White House could also carry out proposals that would remove the fear of deportation and provide work permits for as many as five million illegal immigrants. “Presidents have pretty much complete discretion when it comes to enforcing criminal and other statutory regimes,” said Peter J. Spiro, who teaches immigration law at Temple University. “President Obama can’t start handing out green cards. Short of that, from a legal perspective, there are no serious constitutional or other legal constraints that apply here.”

The White House, however, is already on record suggesting otherwise.

* Watch this ad a Dem House candidate is airing in Minnesota: It depicts insurance industry executives dancing and guzzling champagne at the idea of Obamacare repeal allowing them to go back to the old system. It’s another sign Dems are getting more confident in calling out Republicans over the consequences of repeal.

* Of course, the balance has long been hugely lopsided in the other direction, as a new study shows:

The report, released Friday by nonpartisan analysts Kantar Media CMAG, estimates $445 million was spent on political TV ads mentioning the law since the enactment of the Affordable Care Act in 2010. Spending on negative ads outpaced positive ones by more than 15 to 1.

Americans for Prosperity has already spent over $30 million this cycle, yet the numbers on the ACA just haven’t moved in any meaningful sense.

* Supposed Dead Dem Walking Mark Pryor continues aggressively defending the state’s version of the Medicaid expansion, and his GOP foe has yet to take a position on it, which is odd, since Obamacare repeal is supposed to be such a slam-dunk winner for Republicans.

* Aaron Blake on a new poll that explains why Mary Landrieu’s route to victory is quite literally to get 50 percent plus one, illustrating that while victory for her is very, very tough, it’s doable.

* Jonathan Bernstein is tough on the Democratic push for a constitutional amendment on campaign finance, arguing that it could backfire in policy terms and represents a premature abdication on solving the problem legislatively.

* Max Fisher, an initial skeptic of Obama’s widely-maligned response to the Ukraine crisis, concedes that his hands off policy actually seems to be garnering results, noting that Putin is overreaching and backing off on his own.

* Worth watching: The Progressive Change Campaign Committee is endorsing three House Democratic candidates on the grounds that they support expanding Social Security and are taking on Dems who would cut it, a sign of the left’s determination to make the idea of a Social Security expansion into a key intraparty issue.

* Steve Benen with an important recap: “It’s been a rough week for Republicans and their support for science.” And it’s going to get a lot rougher.

* Meet a new breed of Republican Senate candidates: Ivy League white-shoe types turned salt-of-the-earth heartland Tea Partyers.

* And Politifact rates GOP Rep. Trey Gowdy’s claim that “we were the last flag flying in Benghazi” to be “false.” This doesn’t bode well for suggestions that Gowdy’s select committee will be fully devoted to the search for “truth,” given that “false” is the opposite of “true.”

What else?

Greg Sargent writes The Plum Line blog, a reported opinion blog with a liberal slant -- what you might call “opinionated reporting” from the left.