WASHINGTON — After seven years of emphatic campaign promises, Senate Republicans demonstrated Wednesday they don’t have the stomach to repeal “Obamacare” when it really counts, as the 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Seven Republicans joined all Democrats in rejecting an amendment by Rand Paul of Kentucky that would have repealed most of former President Obama’s health care law, with a two-year delay but no replacement.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 a handful of Republican senators, more than Majority Leader Mitch McConnell could lose in the closely divided Senate.

The result frustrated other GOP 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.

“I think everybody in there, maybe except for one senator, promised their supporters, their voters that they supported repeal of Obamacare,” said Ron Johnson of Wisconsin. “A lot of them said ‘root and branch.’ Now, we’re so far away from that. I’d just remind my colleagues, remember what you promised your voters.”

Yet the outcome was no 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 GOP 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 the Obama law they have reviled for so long.

One possibility taking shape in talks among senators was a “skinny repeal” that would abolish just a few of the key elements of Obama’s law including mandates that everyone purchase insurance and taxes that all GOP senators can agree to oppose.