On Sunday, a poll showed that SPD mayors, favor joining a coalition government with Chancellor Angela Merkel's conservatives. The coalition would boost the prospects of the center-left party backing the alliance in a ballot starting this week. SPD members voted in a postal ballot from Tuesday on whether their party should go ahead with the coalition agreement. Merkel turned to the SPD after her efforts to secure an alliance with the Greens and the pro-business Free Democrats failed in November.