Yesterday, during President Obama’s emotional plea in Newtown for action on guns, Mitch McConnell announced that he would join a group of far right Senators in using a procedural tactic to block the proposal from even being debated on the Senate floor. McConnell’s move is generating much chatter this morning.

But unpack McConnell’s move even just a little bit, and it’s revealed (for now, at least) to be an empty threat — with no clear implications for the outcome of this battle.

For one thing, McConnell’s office is only saying he’ll block the current Harry Reid bill from being debated. That contains Chuck Schumer’s language on expanded background checks, and not the compromise proposal being negotiated by a bipartisan group of Senators. The Post’s Rachel Weiner and Ed O’Keefe asked McConnell’s office whether he would filibuster an eventual compromise, and got this answer:

McConnell aides wouldn’t say whether he would support a modified version of the bill that includes new language negotiated by moderate senators working on a potential compromise.

McConnell’s threat won’t mean anything until we see how he reacts if there is a bipartisan deal on expanding background checks. What’s more, as CNN reports this morning, the emerging compromise would actually water down the proposal by expanding the background check system to cover internet sales and private sales at gun shows — which is to say, sales through commercial portals — while exempting private person-to-person transfers. That will be a lure for the handful of moderate Republican Senators who are at least potentially gettable on background checks — Toomey, John McCain, Susan Collins, Johnny Isakson, Dean Heller.

Additionally, McConnell and his far-right cabal of Senators threatening a filibuster on the motion to proceed — and the 13 overall Senators who are threatening a normal filibuster — are being allowed to get away with a clever ruse. They are threatening to block the overall proposal of gun packages, on Second Amendment grounds, without being pressed on individual provisions in the package. Do these Senators really believe the proposal to make gun trafficking a federal crime — which is in the package — is a threat to people’s Second Amendment rights? Do they really believe expanded background checks threatens those rights, given that few if any of them will say the current background check threatens them? These Senators need to be pressed on these questions.

Finally, there is a winning endgame here for the gun control side that is an outside shot, but cannot be dismissed as impossible. There may be a small body of GOP Senators who is willing to vote to end debate on a proposal that includes modified background checks and the anti-trafficking piece, but will vote No on the final proposal. This could result in eventual passage with a simple majority. Senator Isakson, for instance, said this morning that he supports an up or down vote on the proposals. Senator McCain said over the weekend that his GOP colleagues should not block debate, which means he may be willing to vote to end debate, too, while voting No (or perhaps even Yes) on the final package. (He should be asked about his stance on this.)

Voting to end debate is a way for moderate Republican Senators to be seen doing something for the families of Newtown — as Obama has said, “they deserve a vote” — while ultimately declining to support his reforms. As I said, it’s an outside shot. But it’s not impossible.

* Left gears up to fight Obama over entitlements: A coalition of unions and liberal groups is gearing up for a major fight with the White House over its proposal to include Chained CPI for Social Security in its budget, which will be introduced tomorrow. However, it seems increasingly likely that Republicans won’t accept Obama’s offer — even though it gives them what they themselves say they want.

It remains to be seen whether this exercise in positioning the White House as the compromising party will continue damaging the GOP politically and whether that will make any difference in the long run.

* Gun group runs ad supporting Pat Toomey: With Senator Toomey potentially emerging as a key GOP supporter of expanded background checks, Michael Bloomberg’s Mayors Against Illegal Guns is running a new ad in Pennsylvania applauding Toomey for embracing the idea.

The ad, which points to the strong support among Pennsylvania constituents for background checks, seems designed to give the Senate back, should he be targeted by the NRA or even more extreme groups, as others who have flirted with embracing sensible reforms have.

* Bloomberg’s group to “score” lawmakers: Today, Mayors Against Illegal Guns will roll out a comprehensive new effort to grade lawmakers from “A” to “F” based on their votes on gun legislation. There will be a lot of chortling about this to the effect that a Jewish New York billionaire can’t influence lawmakers in red states. But it’s good to have it made clear that there’s a new outfit out there that will be matching the NRA’s ad spending.

*The NRA’s vastly overrated power: Senator Tim Kaine has published an op ed in a Virginia paper calling on the Senate to allow a vote on the background check and trafficking legislation, with this interesting nugget:

There are those who believe the National Rifle Association and its allies are so powerful that no legislation will pass. But the power of the organization’s leadership is vastly overrated. I’ve run three statewide races in the NRA’s home state. Its leadership campaigned vigorously against me each time, spending nearly $800,000 against me in my 2012 Senate race. I won all my races anyway.

Good to hear a Senator from Virginia saying this. Let’s hope it’s not lost on  the red state Democratic Senators who still have yet to show the courage apparently required to support a proposal backed by nine in 10 Americans.

 * Mitch McConnell joining gun filibuster? Much will be made of McConnell’s quasi-announcement that he will join conservative Senators in blocking the motion to proceed on the gun bill. But his office is only talking about the current Harry Reid bill, which contains a version of the background check that is different from the one being negotiated by a bipartisan group of Senators.

* Dems ratchet up attacks on McConnell: ABC News reports that the Senate Majority PAC, an outside group that tries to elect Dems to the Senate, is rolling out an online ad campaign tarring McConnell as “Washington’s top roadblock.” Its new Web site, “BeltwayMitch.com,” highlights his vote against the Violence Against Women Act.

McConnell’s announcement that he’s joining the gun filibuster should help build the case, though as noted here yesterday, Republicans have reasons not to fear any public backlash on guns.

* On gay marriage, Dem Senators are profiles in courage: Chris Cillizza documents the stampede of Dem Senators to the pro-gay marriage side in the wake of Hillary Clinton’s conversion:

Since Clinton reversed course 14 Senators — 13 Democrats and 1 Republican — have followed suit. The 14 switches over 22 days amounts to a Senator changing position on same sex marriage on average every day and a half. In just two days last month — March 25 and 26 — six Democratic Senators changed their position to support gay marriage.

Amazing. As I’ve noted here before, this is akin to rushing to get in under the wire of history before it’s too late. Better late than never, one supposes.

* And Rick Santorum’s advice on gay marriage: The socially conservative former Senator from Pennsylvania puts his Republican colleagues on notice:

“The Republican Party’s not going to change on this issue. In my opinion it would be suicidal if it did.”

Great advice! This again underscores the aging base’s unwillingness to let the party shed its aura of intolerance by evolving on the issue, even as younger Republicans are now embracing marriage equality.

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.