Last week, Washington D.C. groups reported on two pieces of favorable news for the cause of comprehensive immigration reform. First, Rep. Luis Gutierrez, a Chicago Democrat, said he would draft the outline of an immigration overhaul by Oct. 13, and introduce it soon after.

The immigrant advocates also pointed to a New York Times report that the U.S. Citizenship and Immigration Services agency is preparing for a huge influx of immigrants’ visa applications, which would come if a proposal like Rep. Gutierrez’s passes Congress.

“This is welcome news, wrote Mahwish Khan, at the blog of America’s Voice, a pro-reform lobbying group. “Kudos to the administration for preparing to do the right thing. Now it’s time to get the ball rolling on real immigration reform.”

However, the best sign the ball’s rolling for for reform might have come from elsewhere, not from the immigration bureaucracy, or the lower house of Congress, but the U.S. Senate.

It was in the Senate after all, that the last attempt at an immigration reform collapsed—in 2007.

The encouraging signs came during the Senate Finance Committee haggling over the health care bill. Republicans wanted to add tough immigration-linked language to the bill, including a a five-year wait for legal immigrants wanting to access federal health benefits.

As Frank Sharry wrote in a post, also at America’s Voice, “Democrats … stopped them cold.”

Sen. Robert Menendez, Democrat of New Jersey, said this wait limit was a needlessly harsh imposition on hard-working, law-abiding taxpayers, who in any case supposedly are mandated to have health coverage by the bill.

Why might the Senate Democrats’ push-back be more significant than a bureaucratic preparedness to process visa applications, or Rep. Gutierrez’s bill?

Because the U.S. Senate will ultimately be where comprehensive immigration reform succeeds or fails. It’s in the Senate where Republicans have been aggressively challenging President Obama’s piecemeal immigration fixes (see the Wall Street Journal’s July article, “Senate Resists Changes on Immigration”).

Democratic senators’ willingness to take a public stand in favor of immigrants and a comprehensive reform package, even in the face of a populist furor over illegal immigration, will likely be the crucial factor in the success of reform legislation in 2010. The major sticking point, of course, will be the proposed pathway to legalization for the nation’s estimated 12 million undocumented immigrants.