[Updated 5 p.m. central] Three polls out Friday suggest support for billionaire Donald Trump in South Carolina may be sagging in the days leading up to Saturday’s primary, with either Ted Cruz, Marco Rubio or both closing the gap.

A third poll out today shows Trump maintaining a 15-point lead. He also leads by a comfortable 17-points in a newly released Emerson poll, and by 13.4 points in the RealClear Politics SC poll average the day before the primary.

The good news for Cruz comes from a new NBC News/Wall Street Journal/Marist Poll showing Trump with 28% support among likely Republican voters and Cruz close behind at 23%. Last month, Trump had a 16% advantage over the Texas senator. Marco Rubio lands in third place at 15% support, with Jeb Bush right behind at 13%. South Carolina is thought to be do-or-die for the former Florida governor.

This poll suggests Trump is slipping, especially among voters “who earn less than $50,000 annually, are very conservative, do not practice a religion, men, those under 45 years old, are not married, or are Tea Party supporters.”

The poll was taken after last Saturday’s debate, where a bombastic Trump attacked George W. Bush over 9/11 and was challenged on his continued willingness to fund Planned Parenthood.

As The Stream reported Thursday, another NBC News/WSJ/Marist Poll shows Trump and Cruz in a statistical dead heat nationally, while other national polls indicate Trump has as much as a 17% lead. It would seem the NBC pollsters are doing something significantly different from the polls showing Trump holding onto a large lead over Cruz.

The biggest good news for Rubio comes from an Augusta Chronicle within three points of Trump and five points ahead of Cruz. The poll is the first one conducted completely after the state’s popular governor, Nikki Haley, announced her endorsement of Rubio.

Rubio also finds encouraging news in a recent poll by American Research Group, Inc. ARG’s poll conducted Wednesday and Thursday shows him surging into a solid second place, having gained 8% in five days. Also, the new Emerson poll has Rubio a point ahead of Cruz, a statistical tie.

Here’s a crucial number to notice: The percentage of undecided voters has dropped from 10% down to 3% in South Carolina. With the numbers of the other candidates remaining virtually steady for the week, the ARG poll suggests that the late deciders are breaking sharply towards Rubio.

Trump seems unlikely to lose tomorrow, but if Cruz or Rubio can press him in a state he was supposed to dominate, this could fuel the view that Trump is freshly vulnerable, and attract crucial donor money to the candidate finishing a strong second. The reverse is also true. Candidates finishing a weak fourth, fifth or sixth may see their campaign contributions drying up.

A weak finish from Jeb Bush could prove particularly damaging to the former Florida governor, since he turned in a solid debate performance last Saturday, brought his brother George W. into the state to campaign for him, and was a successful governor in nearby Florida. If he can’t perform well under those conditions, donors and voters may decide it’s time to look elsewhere.