After seven years of emphatic campaign promises, Republicans failed Wednesday to repeal Obamacare, as the U.S. Senate voted 55-45 to reject legislation undoing major portions of Barack Obama's law without replacing it.

Seven Republicans joined all Democrats in rejecting a measure by Republican Sen. Rand Paul of Kentucky that would have repealed most of former president Obama's health-care law, with a two-year delay but no replacement. Congress passed nearly identical legislation in 2015 and sent it to Obama, who unsurprisingly vetoed it.

Yet this time, with a president in the White House who says he's itching to sign the bill, the measure failed on the Senate floor. The Congressional Budget Office has estimated that repealing Obamacare without replacing it would cost more than 30 million Americans their insurance coverage, and that was a key factor in driving away more Republican senators than majority leader Mitch McConnell could afford to lose in the closely divided Senate.

The result frustrated some Republican senators, some of whom expressed disbelief that their colleagues would flip-flop on legislation they had voted for only two years ago and long promised to voters. Of the current Republican senators, only moderate Susan Collins of Maine opposed the 2015 repeal bill.

"Make no mistake: Today's vote is a major disappointment to people who were promised full repeal," said Sen. Ben Sasse of Nebraska. "We still have a long, long way to go — both in health policy and in honesty."

Yet the outcome was hardly a shock in a Senate that's already shown that unity is elusive when it comes to dealing with Obamacare. The real-world implications of repeal have proven sobering to Republican senators answering to voters who've come to rely on expanded insurance coverage under the law.

What the party's senators will end up agreeing on instead is far from clear. Yet they plunged forward with debate toward their unknown goal, pressured by an impatient president. By week's end Republicans hope to reach agreement among themselves, and eventually with the House, on some kind of repeal and replacement for the Obama law they have reviled for so long.

"We have to keep working hard," said McConnell. "We're determined to do everything we can to succeed. We know our constituents are counting on us."

Republicans mull 'skinny repeal' options

One possibility taking shape in talks among Republican senators was a "skinny repeal" that would abolish just a few of the key elements of Obama's law that all Republican senators can agree to oppose.

One version of the skinny bill would repeal mandates on individuals to buy health insurance and on large businesses to offer health insurance to employees. It would also repeal a tax on medical devices.

It would leave the rest of Obamacare intact, falling well short of Republican promises to dismantle the 2010 law.

But in a sign of the general confusion, some said the tactic was aimed chiefly at moving the process forward into the purview of a committee of Senate-House bargainers while others expressed the hope that the House would swallow a "skinny bill" whole, freeing Congress to move on to other issues.

"It's just a vehicle to get into conference [with House Republicans] so it may lead to a broader solution," Sen. Lindsay Graham, Republican from South Carolina, said Wednesday, referring to negotiations with the House on a final bill.

The House narrowly passed its version of a health bill in May. If the Senate passes a different version, the House could simply pass it and send it to the president. Or House and Senate leaders could form a conference committee to work out the differences.

Several Republican senators said this is the path they foresee, which would put off final decisions on what the legislation would eventually look like.

Either way, after weeks spent on the issue including false starts and near-death experiences that have eaten up months of Donald Trump's presidency, the realization was dawning on senators that they may be unable to pass anything more complex for now than a lowest common denominator bill.

"At the end of the day, we've got to start somewhere. This is a start," said Sen. Thom Tillis, Republican from North Carolina.

Trump lashes out at rogue Republican

The day's proceedings began with prodding from Trump, who's proven impatient and inconsistent throughout the health-care debate and yet can claim some credit for resuscitating Senate talks after McConnell essentially declared them dead last week.

The president singled out Alaska Sen. Lisa Murkowski, who'd voted the day before against opening long-awaited debate on the legislation, and also opposed a wide-ranging McConnell amendment Tuesday that offered a replacement for Obamacare and went down to defeat.

Trump tweeted she "let the Republicans, and our country, down."

"I don't really follow Twitter that much," Murkowski remarked to reporters later with a shrug.

Murkowski was also among the seven Republican senators who voted "No" Wednesday on the repeal-only bill. The others were Collins, Shelley Moore Capito of West Virginia, Dean Heller of Nevada, John McCain of Arizona, Rob Portman of Ohio and Lamar Alexander of Tennessee.

In a statement defending his vote, Portman wrote: "We need a rescue plan for Ohio families who are suffering under the status quo, not one that makes the health-care system worse for Ohio families."

Senators were working their way through 20 hours of debate. At week's end, a "vote-a-rama" of rapid-fire voting on a mountain of amendments was expected before moving to final passage — of something.

Internal Republican differences remain over how broadly to repeal the law, how to reimburse states that would suffer from the bill's Medicaid cuts and whether to let insurers sell cut-rate, bare-bones coverage that falls short of the requirements.

While pressure and deal-making helped win over vacillating Republicans to begin debate, they remained fragmented over what to do next. Several pointedly left open the possibility of opposing the final bill if it didn't suit their states.

"It seems the Republican majority is no clearer on what the end game is, because there's no good way out of this," said minority leader Chuck Schumer of New York.