Nearly every one of the Democrats' most vulnerable incumbents split with their party on Friday and voted for a Republican measure to allow Americans to keep their insurance plans under ObamaCare.

All but three of the 26 members of the Democratic Congressional Campaign Committee's Frontline Program — the designation for their most endangered incumbents — voted for the bill.

They joined 16 other Democrats in supporting the measure, which passed the House 261-157. Four Republicans voted against it.

The bill had already picked up four Democratic sponsors: Reps. John BarrowJohn Jenkins BarrowOur democracy can’t afford to cut legal aid services from the budget Dem files Ethics complaint on Benghazi panel Barrow thanks staff in farewell speech MORE (D-Ga.), Mike McIntyre (D-N.C.), Patrick Murphy (D-Fla.) and Kyrsten Sinema (D-Ariz.). All four are top Republican targets in 2014.

Other vulnerable Democrats voting in favor of the bill include Reps. Carol Shea-Porter (D-N.H.), Nick RahallNick RahallLikely W.Va. Senate GOP rivals spar in radio appearances West Virginia is no longer Clinton country Solution needed: Rail congestion is stifling economic growth MORE (D-W.Va.) and Jim MathesonJim MathesonTrump's budget targets affordable, reliable power Work begins on T infrastructure plan New president, new Congress, new opportunity MORE (D-Utah).

The defections reflect the political realities facing Democrats as the botched rollout of the healthcare law has caused widespread public backlash against the law and the party. Democrats have seen the polling advantage they gained following the government shutdown erased in the wake of issues with the law.

President Obama offered his own administrative fix for the dropped plans on Thursday but failed to fully quiet critics who say his solution doesn't go far enough. The president's solution would allow insurance companies to keep offering current plans until after the midterm elections.

Still, House Democrats had expected the defections on the Upton bill to be far higher.

Vulnerable Reps. Ann KirkpatrickAnn KirkpatrickHouse Dems highlight promising new candidates Vulnerable House incumbents build up war chests Cook Political Report shifts 11 House races towards Democrats MORE (D-Ariz.), John Tierney (D-Mass.) and Lois Capps (D-Calif.) all voted against the bill.

Republicans are already out hitting them for their votes. The National Republican Congressional Committee issued releases targeting Kirkpatrick and Tierney. One charges Kirkpatrick "broke her promise," a reference to Obama's erroneous pledge that Americans who like their coverage can keep it.

--This post was corrected at 3:15 p.m. to reflect that Kirkpatrick, Tierney and Capps voted aganst the bill.