You've heard a lot about the Republicans who are standing in the way of immigration reform in the Senate, but some Democrats may not vote for the bill, either.
The Senate will hold its first procedural votes on the Gang of Eight immigration reform bill this week. For the legislation to avoid a potential filibuster, supporters will need 60 senators to back the bill.
"We got virtually every Democrat. We may miss or lose a handful," Senate Majority Leader Harry Reid (D-Nev.) said on Univision's "Al Punto" this Sunday. "We'll get more than 90 percent of the Democrats. All we need is a little help from the Republicans."
But if the bill's supporters have trouble finding enough Republican backers, they be forced to turn to undecided Democrats to cobble together the necessary votes.
Here are a few Democrats who could vote against reform, based on background from groups in favor of the bill:
Sen. Bernie Sanders (I-Vt.)
In 2007, Sanders voted against a comprehensive immigration reform bill over concern about its guest-worker program.
The bill before the Senate this year creates a different type of low-skilled worker visa that was negotiated by business groups and labor unions. But Sanders, a self-described democratic socialist, remains leery of allowing large amounts of foreign workers into the U.S. at a time when unemployment is high.
"I'm very dubious about the need to bring foreign unskilled labor into this country," Sanders, who caucuses with the Democrats, told The Washington Post last month. "These are kids, young high school graduates, and the unemployment rate is just extremely high. I do not understand why they cannot hire those people and need foreign labor."
Sanders is still undecided on the bill. But advocates believe his vote is winnable since he is a strong supporter of a path to citizenship for undocumented immigrants, and because the bill provides agricultural work visas that could benefit dairy farmers in his state.
Sen. Max Baucus (D-Mont.)
Like several of his skeptical colleagues, Baucus is a red-state Democrat who voted against a similar bill in 2007.
But there's something that sets Baucus apart from his colleagues: he's not running for reelection in 2014. That has led to speculation that Baucus could reverse his previous opposition to immigration reform that contains a path to citizenship, since he wouldn't have to face a potential voter backlash next year.
Baucus, however, has hardly given any indication how he'll vote in the end. He's officially undecided and reportedly open to voting for it if the border-security language is strengthened.
The Montana senator has also proven to be a thorn in the side of Democratic leaders in the past. In April, he was one of four Senate Democrats to vote against a bill that required universal background checks for gun purchases, which was a priority for President Obama. Baucus explained his vote in one word.
Two days later, he announced he wouldn't seek reelection.
Sen. Mark Pryor (D-Ark.)
Pryor voted against the 2007 immigration bill and this time around, he's also voicing reservations about voting yes.
In an interview last month with The Wall Street Journal, Pryor predicted that the Gang of Eight bill would pass the Senate. But he remains undecided because he's concerned over the number of visas allotted to construction and high-tech workers.
Electoral politics may also be behind Pryor's hesitation to support the bill. He faces reelection next year in a state that backed Mitt Romney by a 24 percentage-point margin over President Obama and isn't considered friendly to immigration reform.
One thing that could attract Pryor's support is a broad base of support in both parties. He told the Journal that ideally, he would want "north of 70 votes," hinting that could give him the political cover to support it. But that's somewhat of a Catch-22, since gathering that many votes might be difficult without Pryor's backing from the outset.
Sen. Joe Donnelly (D-Ind.)
Donnelly is another red-state Democrat whose vote could be hard to secure.
During his 2010 campaign for Congress, Donnelly ran an ad in which he said on camera that he wants to "deport illegals who commit felonies and eliminate amnesty, because no one should ever be rewarded for breaking the law." He also voted against the DREAM Act in 2010.
Donnelly is officially uncommitted on the Gang of Eight bill before the Senate, which contains a path to citizenship. And he's been under pressure from groups both for and against the bill to vote their way.
So far, Donnelly hasn't indicated how he'll decide. But judging from his past positions, it's not looking great for immigration reform supporters.
Others Democratic senators to watch: Heidi Heitkamp (N.D.), Mary Landrieu (La.), Kay Hagan (La.), Jon Tester (Mont.)