Thiruvananthapuram, Oct 1 (IANS): Ahead of crucial five assembly by-elections to be held on October 21, the Congress-led United Democratic Front (UDF) in Kerala lost its star campaigner in two-time former Chief Minister Oommen Chandy, who, on Tuesday morning left to the United States for medical treatment of a throat ailment, the party source said.

Speaking to IANS, his closest aide said that for a while now he has been troubled with a throat ailment.

"He was under treatment here for a while but his family decided to take him to a hospital in the US for a complete check up. Today (Tuesday) morning he left to Dubai, where his younger daughter will join him on his US trip," said the aide, who did not wish to be named.

Chandy, who will turn 76 on October 31, is currently the biggest crowd puller in Kerala politics, and is known for his patience in hearing each and every person who comes to meet him and carries no airs of his exalted stature.

"He was not willing to go at this juncture, but with the family unwilling to relent, he decided to go. He has made it very clear that he will return at the earliest and has a return booking on October 6. But, his return will depend on the doctor's advice. If they suggest further treatment, then it might have to be done there," added his aide.

The Congress-led UDF camp is a bit jittery, after the shock defeat in Pala assembly seat at the hands of the Left Democratic Front (LDF). The seat was held by the UDF since 1965.

Now, among the five assembly seats which go to the bypolls on October 21, four of them are presently held by the UDF.