ROBERT SIEGEL, host:

From NPR News, this is ALL THINGS CONSIDERED. I'm Robert Siegel.

Tomorrow on C-SPAN, it will be �Saturday Night Live� at the U.S. Senate. A crucial evening vote is expected to cap an all-day debate on overhauling health care. Democrats need 60 senators voting yes to keep a newly unveiled bill moving forward. They have 60 members in their caucus, but it's been a struggle to get them all lined up. Several remain strongly opposed to the bill's public insurance option, even though it's been scaled back, as NPR's David Welna reports.

DAVID WELNA: The public option in the Senate's bill may disappoint some supporters. It allows entire states to opt out of such a government-backed insurance plan. And rather than paying health care providers the same relatively low rates paid by Medicare, it would have to negotiate those rates just as private insurers do. Still, Senate Democrats who strongly back a public option insist the bill's version will nonetheless make a big difference. Here's New Mexico's Tom Udall.

Senator TOM UDALL (Democrat, New Mexico): The first thing that we're trying to accomplish with a public option is to inject that competition into the market, to have insurance companies be competing and this public option is going to help drive that cost down, drive it down in a dramatic way.

WELNA: But the Congressional Budget Office says the Senate's public option will have higher premiums than those of private insurers since it's expected to enroll more people with costly health problems. Republican Leader Mitch McConnell pointed out today that this public option would actually be more expensive than private plans, and McConnell sees that as a red flag.

Senator MITCH MCCONNELL (Republican, Kentucky; Senate Minority Leader): So, clearly the only way it could have a positive impact on the cost of insurance would be to subsidize cost, ration care and undercut private insurers.

WELNA: And New Hampshire Republican Judd Gregg predicts employers will eventually have to drop private insurance plans because of rising costs, pushing more and more people into the public option.

Senator JUDD GREGG (Republican, New Hampshire): This is an exercise in having the federal government basically get control over all health care. And it's being done in an incremental way. They're setting up a scenario here that won't be immediately apparent to people, but as we move through the years, it'll become apparent.

WELNA: For now, though, the CBO expects only three to four million people would choose the Senate's public option. Majority Leader Harry Reid insists he's fine with such limited enrollment.

Senator HARRY REID (Democrat, Nevada; Senate Majority Leader): Under any plan that I've seen, the most was 5.5 million. So, we're right in line with what would be an adequate and, I think, very powerful, robust public option.

Senator DICK DURBIN (Democrat, Illinois): I wish it were a bigger public option, from my own point of view.

WELNA: That's the Senate's number two Democrat, Dick Durbin. He says the realities of the Senate require a more modest public option than what he'd envisioned.

Sen. DURBIN: The realities are we need 60 votes on the Democratic side and there are some who even oppose any form of public option. Harry Reid is trying to find that sweet spot, that position that brings 60 votes together. And I'm sure each of us, including Senator Reid and myself, could write a bill more to our liking and maybe more effective in some areas, but we understand that this is the art of the possible.

WELNA: And it's indeed looking increasingly possible that Democrats will get the 60 votes they need tomorrow. Nebraska's Ben Nelson, who opposes a nationwide public option, announced today he intends to vote with fellow Democrats tomorrow to bring up the bill. Louisiana's Mary Landrieu and Arkansas' Blanche Lincoln, who also oppose a federally funded public option, have yet to declare their intentions. But Democratic leaders appear confident that even without the help of a single Republican, they'll win this bill's first big test vote.

David Welna, NPR News, the Capitol. Transcript provided by NPR, Copyright NPR.

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