Republican presidential candidate Rudy Giuliani interrupted his campaign and checked in to a Missouri hospital with flu-like symptoms, according to media reports on Thursday.
The former New York City mayor called off a campaign flight from Missouri to New York because of illness, the Los Angeles Times reported.
After consulting by phone with his personal physician, the newspaper said Giuliani entered Barnes Jewish Hospital in St. Louis for observation and was to stay there at least through the night.
A campaign spokesman told the newspaper Giuliani developed flu-like symptoms earlier on Wednesday, but continued campaigning until the symptoms worsened in the evening.
Giuliani has seen his status as the front-runner for the Republican nomination erode. An NBC News/Wall Street Journal poll released on Wednesday said he has fallen 13 points since November and is now tied with former Massachusetts governor Mitt Romney nationally in the race for the Republican nomination.
Giuliani had been the clear leader in all previous NBC/Journal polls and led the field with 33 per cent support in the survey last month.
The state-by-state process starts on January 3 in Iowa for choosing candidates in each party for the November 2008 election.