The bipartisan immigration reform bill gained a bit more Republican support recently, but it also lost a vote Democrats have been counting on.

Republican Senator Kelly Ayotte of New Hampshire voiced her support for the immigration bill in an op-ed on her website, but the length of her statement demonstrates her need to preemptively defend her position against attacks from the right.

"For too long, politicians on both sides of the aisle in Washington have failed to lead on this issue. And no doubt there will be naysayers in this debate who will continue to make excuses for inaction. But I ran for the Senate to make tough, independent decisions to strengthen our country, and that's what it will take to solve our nation's immigration problems," Ayotte wrote.

"This week, the Senate will take up immigration reform legislation that recently passed the Judiciary Committee on a bipartisan basis. After careful review of this bill, and after meeting with Granite Staters, I will support it and plan to vote for amendments offered to strengthen it," she wrote.

Ayotte came under fire earlier this year when the National Rifle Association and gun lobbyists pressured her to vote against the Senate's popular proposal requiring background checks for all firearms purchases.

In addition, the bill won support from an unlikely source, Republican strategist Karl Rove's Super PAC Crossroads GPS. That support comes with plenty of caveats, but the demands aren't far off from those of more moderate Republican senators.

"The Senate immigration bill needs an 'extreme makeover' before we can say it really protects our borders and our workers, but it's important that Congress move forward on it and not just throw up its hands," said Crossroads GPS CEO Steven Law.

But the death of Democratic Senator Frank Lautenberg of New Jersey leave the bill down a vote in the count. Lautenberg was a staunch supporter of immigration reform, but Republican Governor of New Jersey Chris Christie appointed Jeff Chiesa to the seat.

Chiesa will hold that position until a special election in October, so he will likely cast a vote on the immigration bill. His position on it is unclear for now, but he has said his main concern is border security.

With Chiesa's appointment, the Democratic caucus shrinks to 54, six votes shy of overriding a filibuster. They'll need every Republican they can get.