Republican presidential candidate Steve Forbes briefly left the Iowa campaign trail today to attend a funeral — his wife, Sabina, had to fill in at stops in Fairfield and Ottumwa. During a telephone interview on K-S-C-J radio in Sioux City, Forbes hammered away at front-runner George W. Bush’s tax record.Forbes proposes abolishing the I-R-S and instituting a 17-percent “flat tax” on income.Bush proposes an across-the-board reduction in income tax rates, as well as raising deductions so more low-income Americans pay no tax at all.