At The Washington Post, Greg Sargent uncovers letters from Sens. Patty Murray (D-Wash.) and Elizabeth Warren (D-Mass.) opposing, at least for now, new Iran sanctions. (I wrote this week about how the bid to build a veto-proof majority for the sanctions legislation has stalled.)

Sargent does some math and figures that with these two, “the number of Dems against a vote has comfortably surpassed the number who want one.”

I count 19 members of the Senate Democratic caucus opposed to a vote, versus 15 who might be assumed to support one, with 21 not accounted for.

Here’s how I got there.

There are 16 Democrats out of the 59 Senators co-sponsoring the bill, including lead sponsor Sen. Robert Menendez (D-N.J.). (On Dec. 19, when the bill was launched, 15 Democrats signed on; Sen. Michael Bennet of Colorado is the sole Democrat to have signed onto the bill since Congress returned to work this month.) Subtract from those 16 Sen. Richard Blumenthal (D-Conn.), who now opposes advancing the bill while talks are underway between Iran and the major powers. The White House and sympathetic Democrats say the bill could scuttle the talks; backers of the bill say new sanctions would enhance the U.S. hand in the talks.

So that’s 15 one might assume still back advancing the bill.

As Sargent notes, there are 10 committee chairs who signed a letter opposing the bill. In addition to those, there are another nine senators who in recent weeks have told interlocutors they oppose advancing the bill for now: There are Murray and Warren, plus Blumenthal. There are another four listed in this Huffington Post roundup. Sen. Bernard Sanders, the Vermont independent who caucuses with Democrats, is listed here. And I’ve heard from Rhode Island Jewish officials that Sen. Jack Reed (D-R.I.) is opposed to advancing the bill now.

The White House is competing hard with backers of the bill, including leading pro-Israel groups, for the remaining 21 members of the Democratic caucus. Among them are key players in states with substantial Jewish communities, like Sen. Harry Reid (D-Nev.), the majority leader; Sen. Dick Durbin (D-Ill.), the assistant majority leader; and Sen. Sherrod Brown (D-Ohio.).

Here are some other breakdowns. Of the Senate’s seven Democratic leaders, two are signed on to the bill, two have said they won’t advance it, and three others we’re not sure. The breakdown of committee chairs is 13 against, four for and three not known.

Of the ten Jewish Democrats, six (Dianne Feinstein-Calif., Barbara Boxer-Calif., Ron Wyden-Ore., Carl Levin-Mich., Blumenthal and Sanders) oppose advancing the bill now, two favor it (Ben Cardin-Md. and Schumer) and two have yet to say (Franken-Minn. and Schatz-Hawaii).

Among Republicans, 43 out of 45 back the bill; the holdouts are Sen. Jeff Flake (R-Ariz.) and Sen. Rand Paul (R-Ky.).

Ron Kampeas is JTA’s Washington bureau chief, responsible for coordinating coverage in the U.S. capital and analyzing political developments that affect the Jewish world. He comes to JTA from The Associated Press, where he worked for more than a decade in its bureaus in Jerusalem, New York, London and, most recently, Washington. He has reported from Northern Ireland, Afghanistan, Bosnia and West Africa. While living in Israel, he also worked for the Jerusalem Post and several Jewish organizations.