Former Vice President Joe Biden’s embrace of the Hyde amendment, prohibiting federal funds from being used for abortion, combined with a new plagiarism controversy have created the most challenging week for the Democratic front-runner since he entered the race for the White House earlier this spring.

Biden has led public opinion polls by double-digits since announcing his campaign but will now face new questions about whether he can retain his lead.

Democratic rivals who slammed Biden’s support of the Hyde amendment on Wednesday will be looking to use his remarks and position on abortion, in particular, to close the gap while casting the former vice president as out of step with the party.

And while the story that Biden’s campaign took lines from outside sources for his climate plan may not damage him as much in the Democratic primary, it does raise the specter of his 1988 presidential run — which ran aground after it was revealed that Biden plagiarized speeches from a British politician.