VIDEO: Scott Walker announces end to his presidential campaign

Saying that Republicans need a "a positive, conservative alternative to the current frontrunner," Wisconsin Gov. Scott Walker suspended his presidential campaign on Monday.

"Today I believe that I am being called to lead by helping to clear the field in this race so that a positive, conservative message can rise to the top of the field.

"With this in mind, I will suspend my campaign immediately. I would encourage other Republican presidential candidates to do the same, so that the voters can focus on a limited number of candidates who can offer a positive, conservative alternative to the current frontrunner.

"Sadly, the debate taking place in the Republican party today is not focused on that optimistic view of America. Instead, it has drifted into personal attacks," Walker said.