Are Republican Senators Being Controlled Behind The Scenes?

Earlier today, President Trump delivered accurate and necessary words to Republican senators. According to reports from The Hill, President Trump made the following statements:

“We shouldn’t leave town until this is complete. We should hammer this out and get it done. We can repeal, but we should repeal and replace. Frankly I don’t think we should leave town unless we have a health insurance plan, unless we can give people great health care. Because we’re close. We’re very close. Any senator who votes against debate says you are fine with ObamaCare. I’ve been here six months. I’m ready to act, pen in hand, believe me. I’m sitting in that office. I have pen in hand. You never had that before.”

While the President’s words may have been a tough pill for GOP senators to swallow, they needed to hear them. He makes very valid points. Why did Republican have little to no trouble with getting votes to repeal the ACA when President Obama was in office and they knew he would veto any bill they proposed?