Senate Democrats easily blocked an amendment to repeal Obamacare in a vote that conservatives decried as a disingenuous move by the GOP leadership to appeal to its base.

The 49-43 defeat of the Obamacare-killing provision now sets up a showdown tomorrow between a group of Senate conservatives and their GOP leadership.

Republicans control only 54 votes, making it a foregone conclusion that Democrats would muster the 41 votes needed to kill the provision.

The amendment was offered by Sen. Majority Leader Mitch McConnell, R-Ky., as part of a bill to authorize highway projects for the next six years.

Conservatives are angry that they have not been allowed to offer other amendments that stood a chance of passage, including one that would strip taxpayer dollars from Planned Parenthood.

Sen. Mike Lee, R-Utah, intends to offer the Obamacare amendment a second time, after debate ends on the highway bill, which under Senate rules would require only a 51-vote threshold for passage.

But first the amendment must be ruled germane to the highway bill, and that is something GOP leaders are likely to oppose.

Lee is planning to call for a vote to overturn the leadership's ruling, and this will set up a potentially dangerous vote for Republican senators on the issue of repealing the law.

Conservative groups, including Heritage Action, are calling on lawmakers to back Lee when he offers his amendment.

Heritage announced that the vote for McConnell's 60-vote Obamacare repeal would not be part of the conservative scorecard, but Lee's provision would be counted.

"No Republican Senator will receive any public praise for their vote on the McConnell show vote," Heritage Action announced.