Who pays for Obama's trip on behalf of Coakley? also, who paid for Clinton's? Taxpayers?

Who pays for expenses incurred by Pres. Obama to Boston on behalf of Coakley, such as secret service, jet fuel, police, etc. and who paid for Clinton's trip on her behalf for the same? Obama and Clinton or the taxpayers?

Taxpayers. The taxpayers pay for every single thing the government does, regardless of whether it benefits the tax payers or not. Tax money is keeping the government running.