Is it possible for a bill repealing Obamacare to not be conservative enough?

It appears so.

Presidential candidates Ted Cruz (R-Texas) and Marco Rubio (R-Fla.) joined their Senate colleague Mike Lee (R-Utah) on Thursday to announce they do not support a House bill to be voted on Friday that would repeal large portions of Obamacare, defund Planned Parenthood and reiterate Republican plans for deep spending cuts.

The senators argued the bill does not completely wipe Obamacare off the books and therefore does not go far enough.

“Each of us campaigned on a promise to fully repeal Obamacare and a reconciliation bill is the best way to send such legislation to President Obama’s desk. If this bill cannot be amended so that it fully repeals Obamacare pursuant to Senate rules, we cannot support this bill,” Cruz, Rubio and Lee said in a statement Thursday.

Their opposition means that the legislation may be in trouble in the Senate if it passes the House, where the vote on Friday may also be tight.

The influential conservative group Heritage Action is calling on members to reject the bill, echoing the rationale put forward by Cruz, Rubio and Lee.

“This bill will not restore Americans’ health care freedom because it leaves the main pillars of the law in place,” Heritage said. “GOP leaders are violating an explicit promise made in the budget and walking back on their public commitment to fully repeal Obamacare.”

Reconciliation bills are considered under special rules that require only a simple majority for passage, meaning the legislation cannot be filibustered in the Senate.

Conservatives have eyed the process as the best way to get around Democratic filibusters and force President Obama to veto legislation repealing his signature domestic policy achievement — a political confrontation they are eager to have.

The use of these special budget rules recently also became entangled in the debate over whether to defund embattled women’s group Planned Parenthood.

With conservatives threatening to vote against legislation to prevent a government shutdown because it would provide funds for Planned Parenthood, House GOP leaders said they could use the reconciliation process to take on the organization.

Now that plan is running into resistance because of how the legislation will address Obamacare.

While reconciliation is a powerful tool, it is limited. It is only intended to address policies that have a direct impact on spending or taxes, meaning it is questionable to what degree it can be used to go after broader policies.

Cruz, Rubio and Lee said Republicans should test these limits.

“With millions of Americans now getting health premium increase notices in the mail, we owe our constituents nothing less,” the trio said of seeking a full repeal of the law.