BERLIN, Aug 8 (Reuters) - The co-leader of Germany"s Greens on Sunday defended the party"s candidate for chancellor at next month"s federal election, and brushed off suggestions that he should replace her after she made a string of costly mistakes. The ecologists briefly surged in the polls to overtake Chancellor Angela Merkel"s conservative bloc after they named Annalena Baerbock as their chancellor candidate in April, but have since waned. Baerbock"s error-strewn campaign has included mistakes in her resume and a scandal over a Christmas bonus payment that she failed to declare to parliament. Baerbock has also said that sexist scrutiny is holding her back. read more "Ms Baerbock is suitable for the office of chancellor, and our task is to ensure that the Greens are strong," the party"s co-leader, Robert Habeck, told broadcaster ZDF in an interview. Asked whether the Greens should replace Baerbock with him as their chancellor candidate, Habeck responded: "No, that"s not a debate." Adding to the Greens" woes, the party will be excluded from the ballot in the state of Saarland in the Sept. 26 national election due to irregularities in the selection of regional candidates following internal squabbling. "The Greens campaign had a few problems but ... I"m looking forward to August and September," said Habeck, who is party co-leader with Baerbock. "Everything is possible." An opinion poll published earlier on Sunday showed the left-leaning Social Democrats (SPD) drawing level with the Greens on 18%, behind Merkel"s conservatives on 26%. Merkel, in power since 2005, plans to stand down after the election. read more The INSA poll showed that in a hypothetical direct vote for chancellor, SPD candidate Olaf Scholz was well ahead, with 27% support. Conservative Armin Laschet languished on 14%, one point ahead of Baerbock, on 13%. The Greens presented an "emergency climate protection programme" on Tuesday, aiming to reset their campaign. read more