MONROVIA, Liberia — Health workers manned polling stations across Liberia on Saturday as voters cast their ballots in a twice-delayed Senate election that has been criticized for its potential to spread the deadly Ebola disease. Originally scheduled for October, the vote was pushed back to Dec. 16 as Liberia struggled to contain the Ebola epidemic, which has killed nearly 3,300 people in the country. Earlier in the week, Assistant Health Minister Tolbert Nyenswah warned that anyone running a temperature higher than 98.6 degrees Fahrenheit could be removed from the line and sent for screening. On a visit to Liberia on Friday, U.N.