Biden rival proposes ‘no-spoiler pledge’ in order to take on Trump in November

It appears you're talking about a proposal made by one of President Joe Biden's political rivals. The 'no-spoiler pledge' likely refers to a commitment where third-party candidates or those from the same party agree not to divide the vote, thereby reducing the chances of their mutual opponent (in this case, presumably Donald Trump) winning the election due to a split vote. However, your question doesn't mention who this rival is. Could you provide more specifics so that I can give you a detailed answer?