US presidential candidate who suspended his presidential bid in April, Rick Santorum, finally gave his ex-rival Mitt Romney his full endorsement and support after he once called Romney \"the worst Republican in the country\". Santorum, the former Pennsylvania senator wrote in a late night email to his supporters released late on Monday \"he has my endorsement and support to win this the most critical election of our lifetime.\" He said his support to Romney came after he became convinced that his ex- rival was committed to conservative causes upon a one-on-one meeting they had on Friday to discuss Santorum\'s concerns, according to Financial Times and USA Today. \"The primary campaign certainly made it clear that governor Romney and I have some differences, but there are many significant areas in which we agree.\" Santorum wrote. He said that they both agreed on some issues as the need to \"lower taxes, smaller government\" and that \"abortion is wrong\". \"He clearly understands that having pro-family initiatives are not only the morally and economically right thing to do, but that the family is the basic building block of our society and must be preserved.\" Santorum clarified. \"I have no doubt if elected he will work with a Republican Congress to repeal it and replace it with a bottom up, patient, not government driven system,\" Santorum wrote in the email. Santorum stressed in his email that one of the reasons he was backing Romney was the need to defeat the current US president Barack Obama in the upcoming November election. \"Above all else, we both agree that President Obama must be defeated,\" he said.