US Republican presidential candidate Michele Bachmann has ended her White House campaign. The Tea Party favourite made the announcement in Des Moines, Iowa, where she finished a disappointing sixth in the state's caucuses on Tuesday. The Minnesota congresswoman's withdrawal from the field leaves six others in the presidential race. They are vying to become the Republican nominee to challenge President Barack Obama for the White House in November. Former Massachusetts Governor Mitt Romney won Iowa's caucuses by a wafer-thin margin over former Pennsylvania Senator Rick Santorum. Texas Governor Rick Perry, who finished fifth, returned to his home state to consider his next step. But in a sign that he is not about to bow out, he tweeted on Wednesday: "Here we come South Carolina!!!" After cancelling her own campaign trip to South Carolina, Mrs Bachmann, 55, told a news conference on Wednesday morning: "Last night the people of Iowa spoke with a very clear voice and so I have decided to stand aside." Mrs Bachmann did not indicate whether she would endorse any other candidate, but said: "I believe that we must rally around the person that our country and our party and our people select to be that standard bearer." She also pledged she would "continue to be a strong voice" in the race to challenge President Obama, and would "stand and fight for the country". Mrs Bachmann said she had "no regrets" about her candidacy and that she had campaigned with integrity. She was briefly the front-runner of the race in August, and had aimed to capture the evangelical Christian vote in Iowa. But two senior backers left her cash-strapped Iowa campaign last week, amid dire opinion-poll ratings. Correspondents say her withdrawal could benefit Mr Santorum since he attracted the support of religious voters in Tuesday's vote.