Markus Junianto Sihaloho – Boediono, incumbent President Susilo Bambang Yudhoyono's running mate, formally turned down an offer from the chairman of the Prosperous Justice Party to accompany him on a minor hajj pilgrimage ahead of Wednesday's election, a spokesman for Yudhoyono's campaign said on Thursday.

The recent offer from Tifatul Sembiring, chairman of the Islam-based party known as the PKS, again put the spotlight on perceptions that Boediono lacks Muslim credentials.

The PKS, a key partner in Yudhoyono's Democratic Party-led coalition, needs help to bring their members into the coalition, and the pilgrimage was seen as a way to do that, a PKS source told the Jakarta Globe.

"It would be considerably easier for us to secure solid support from the members of our party if [Boediono] showed that he was a good Muslim," said the source, who declined to be identified. "Our members are extremely critical, you know."

Yudhoyono campaign spokesman Rizal Mallarangeng said on Thursday that Boediono declined the PKS offer and would instead leave on Monday for Yogyakarta, where he lectures at Gadjah Mada University. "Boediono will stay in Yogyakarta and will vote at a polling station [there]," Rizal said.

Boediono's wife, Herawati, recently became the target of a smear campaign, after PKS deputy secretary general Zulkieflimansyah said that a number of PKS members were considering the possibility of voting for current Vice President Jusuf Kalla and his running mate, Wiranto, because their wives regularly wore headscarves.

Later, copies of an article stating that Herawati was a Catholic were circulated at a campaign rally for Kalla. On Thursday, Herawati attended a mass Islamic prayer at the Al Bina Mosque in Senayan, Jakarta.