Senate Republican leaders have decided to delay a floor vote on their plan to repeal and replace Obamacare until after the July 4 recess because they've failed to secure enough votes to back it so far.

Republicans need 51 votes to pass the legislation, but one vote can be Vice President Mike Pence's tie-breaking vote. And assuming all Democrats vote against it, Republicans can only afford two defections. The Senate currently has 52 Republicans and 48 Democrats.

Before senators consider the measure itself, they'll have to vote on a motion to proceed. Republicans can only lose two votes on this motion in order to advance the bill. After the nonpartisan Congressional Budget Office (CBO) released its score of the Senate bill Monday, it appeared that the bill did not have the support necessary for the procedural motion.

The 142-page measure, would end Obamacare's penalties for people who don't buy insurance, cut back an expansion of Medicaid, but would keep protections for people with pre-existing conditions, compared to the House-passed bill. It would provide tax credits, based on income, age and geography, which would make more money available to lower-income recipients to help them buy insurance. This differs from the House bill, which tied its tax credits only to age. Obamacare taxes would be repealed under the bill. The Senate bill would provide for expanded tax-free Health Savings Accounts, and it would also eliminate federal funding for Planned Parenthood for one year.

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Hours after text was revealed, Sen. Rand Paul, R-Kentucky, announced with three other Senate Republicans that they opposed the bill in its current form because it doesn't go far enough in repealing President Obama's health care law. A day later, Sen. Dean Heller, R-Nevada, became the fifth Senate Republican to reject the measure. Sen. Susan Collins, R-Maine, came out against it after the CBO score.

After leadership announced that the vote was delayed, three more Senate Republicans said they opposed the original version: Jerry Moran of Kansas, Rob Portman of Ohio and Shelley Moore Capito of West Virginia.

Senate Majority Leader Mitch McConnell, R-Kentucky, has a challenging road ahead as he faces trying to bridge the divide between conservatives who want a more robust repeal of Obamacare and moderates who are wary about phasing out Obamacare's Medicaid expansion.

Here's a list of Senate Republicans who oppose the bill in its current form:

Sen. Rand Paul, R-Kentucky

Sen. Ted Cruz, R-Texas

Sen. Mike Lee, R-Utah

Sen. Ron Johnson, R-Wisconsin

Sen. Dean Heller, R-Nevada Sen. Susan Collins, R-Maine Sen. Jerry Moran, R-Kansas Sen. Rob Portman, R-Ohio Sen. Shelley Moore Capito, R-West Virginia

Even if McConnell is eventually successful in getting it through the Senate, the process won't be over. The House and Senate would then have to reconcile their two bills and pass a final agreement in each chamber before it can be sent to President Trump's desk.

CBS News' John Nolen and Alan He contributed to this report.