How key a role?
"He's basically the defense, the prosecution, the judge, the jury and the hangman in this scenario," said Sen. Judd Gregg, the ranking Republican on the Senate Budget Committee.
The fix-its, passed by the House of Representatives Sunday night, were necessary to get House Democrats to support the bill. And Frumin, as parliamentarian, decides what is germane, under Senate rules.
In other words, he decides which amendments require 51 votes, which Democrats have, and which amendments require 60 votes, which they don't.
Democrats won the first battle late Monday night when Frumin agreed with them that the bill does not affect Social Security. Had he sided with Republicans, the entire set of fix-its would have been ruled out of order and Democrats would have had to muster 60 votes -- they are at least one short -- to bypass him.
That move brought criticism from some Republicans, who point out that Frumin, as a Senate employee, is nominally employed by the majority party.
But Republican leaders have not yet said Frumin is anything but an unbiased umpire.
"We'll have views about that, I suppose, as we move along. We'll see what the parliamentarian rules and whether he becomes a player in this exercise or truly a referee, an umpire," said Minority Leader Mitch McConnell of Kentucky.
Frumin has worked on Capitol Hill since 1974 and in the Senate parliamentarian's office since 1977. He has been appointed twice as parliamentarian -- once by Democrats and once by Republicans.
The first time was in 1987, when Democrats took control of the Senate. Then he was appointed in 1995 by Senate Majority Leader Trent Lott, who became frustrated with then-parliamentarian Bob Dove over a ruling.
Frumin can be seen whenever the Senate is in session, on C-SPAN 2. During the long hours of "quorum call" between speakers or when a vote is called, Frumin can be seen on the left side of the screen.
When the presiding officer says something in halting parliamentary parlance, odds are that Frumin is just off screen, whispering up to tell the lawmaker what to say.
He should know. The official rulebook for the Senate is "Riddicks Senate Procedure," but Frumin updated the original version and is now listed as author.
Under reconciliation rules, only 20 hours of debate are allowed. During that time, Republicans and Democrats can offer an unlimited number of amendments, none of which are filibusterable and all of which get a vote. The scope of these amendments should hue to the Finance and the Health, Education, Labor and Pension committees -- which is just about everything under the sun.