The Senate on Tuesday cleared a key procedural hurdle on an extension of long-term unemployment insurance, with six Republicans voting to move forward -- just enough to get it to 60 votes and set it up for likely passage in the upper chamber.

So who joined with Democrats to pass the bill, and why?

Here's the breakdown:

Who voted for it?

54 of 55 Senate Democrats

Sen. Dean Heller (R-Nev.) -- a co-sponsor of the bill, his state is tied for the highest unemployment rate in the country (along with fellow co-sponsor, Rhode Island Democrat Jack Reed) at 9.0 percent. It is also tied for the second-highest long-term unemployed, according to the Joint Economic Committee. He was also the sixth-most moderate GOP senator in 2012, according to National Journal Vote Ratings.

Sen. Kelly Ayotte (R-N.H.) -- 10th-most moderate GOP senator in 2012

Sen. Dan Coats (R-Ind.) -- 16th-most moderate GOP senator in 2012

Sen. Susan Collins (R-Maine) -- second-most moderate GOP senator in 2012

Sen. Lisa Murkowski (R-Alaska)  -- third-most moderate GOP senator in 2012

Sen. Rob Portman (R-Ohio) -- 14th-most moderate GOP senator in 2012

Apart from Heller, none of these GOP senators' states rank among the leaders in long-term unemployment. Ohio is next after Nevada, and it is tied for 17th.

Who voted against it

37 of 45 Senate Republicans

Who didn't vote

Sen. Mark Begich (D-Alaska)

Sen. Orrin Hatch (R-Utah)

Sen. John Thune (R-S.D.)